The function `GetMappedAction()` is added to the vtkVRInteractorStyle
base class through MR-10784.

See https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10784

Removes "GestureEnabledButtons" ivar that became obsolete following
these commits:
* c5c6d6f ("BUG: Restore complex gesture support", 2023-01-29),
* 22eba9f ("BUG: Fix integration with updated Slicer event delegation and VTK OpenVR API (KitwareMedical#131)", 2023-12-21)
* 0fa6102 ("BUG: Ensure handling of gesture triggers the "End" event", 2023-12-20)
* 512efe6 ("BUG: Do not report "Unrecognized device" if handling complex gesture", 2023-12-20)

For reference, it was originally introduced in 43bef4b ("ENH: Make trigger
button configurable", 2019-01-11).

The function `GetCurrentGesture()` is added to the vtkVRRenderWindowInteractor
base class through MR-10786.

See https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10786

Since OpenXR and OpenVR runtime each require their own instance of
interactor style, this commit relocates is a step toward reducing the
amount of code that will be duplicated.

Since OpenXR and OpenVR runtime each require their own instance of
interactor style, this commit is a step toward reducing the amount
of code specific to the interactor.

The is made possible after the following vtkOpenVRRenderWindowInteractor
updates:

* Declare AddAction() functions as virtual.
  See https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10785

* Mark ComplexGesture recognition functions as public.
  See https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10786

For reference, the "GestureButton" configuration functions were
introduced through these commites:
* 43bef4b ("ENH: Make trigger button configurable", 2019-01-11)
* e268168 ("ENH: Add python-accessible functions to capture vr
  controller events, associate buttons with gestures and enable/disable
  interaction.", 2019-05-30)

Update the RenderWindowInteractor to use the recognizer. This will allow
to have dedicated interactor for OpenVR and OpenXR runtime wihout any
code duplication.

Following 22eba9f (BUG: Fix integration with updated Slicer event
delegation and VTK OpenVR API), the VirtualReality interactor style
derives from `vtkOpenVRInteractorStyle` and all the upstream
capabilities are now available.

Also removes redundant call `InteractorStyle->SetInteractor(this->Interactor)`
Calling `Interactor->SetInteractorStyle(this->InteractorStyle)` is sufficient.

Update the InteractorStyle to use a delegate implementing the common
logic related to processing of the "Pinch3D" complex gesture, handling of
the "PositionProp" interaction and update of the view magnification. This
will allow to have dedicated interactor styles for OpenVR and OpenXR
runtime without code duplication.

Group headers and remove unused ones.

Consistently use "VR [Logic|MRML|MRMLDM|Widgets] includes" comment to
introduce headers from this extension.

Re-order include groups and sort alphabetically within groups.

Remove `vr::TrackedDevicePose_t` forward declaration that became
obsolete following commit 0c8c2e8 ("ENH: Decouple update of transform
node matrix and attributes", 2023-12-26)

…fier

…ossible

This is done anticipating subsequent refactoring in which the computation
of the ActionManifestPath will be moved to the logic.

Update VirtualReality logic adding `ComputeActionManifestPath()` utility
function and update VirtualRealityView to compute the path based on the
XR runtime.

To support computing the path based on the module install state, the
`ModuleInstalled` property was also added.

…base on XRRuntime

This commit streamlines the process of creating a RenderWindow in the
qMRMLVirtualRealityView class by making several improvements:

- Reorganize the update of QCursor in the `createRenderWindow()` function
  around the time-consuming `RenderWindow->Initialize()` call.

- Set the view node's Error status directly within `createRenderWindow()`,
  and check for view node errors before returning from `updateWidgetFromMRML()`.

- Enhance `destroyRenderWindow()` to gracefully handle calls without
  instantiated objects.

- Update `createRenderWindow()` to set a view node error if the XR runtime is
  undefined and RenderWindow creation did not occur.

…erWindow

Since we systematically attempt to initialize the runtime if it is
"UndefinedXRRuntime" or if it has changed, this commit also adds support
for checking for the maximum initialization attempts and avoid recursion.

Users can now conveniently select and update the current XR Runtime.

This commit removes the explicit dependency on the "openvr.h" header in the
TransformWidget. However, it's essential to note that tracking results
are not standardized, and the status will consistently be reported as
"off" for XR runtimes other than OpenVR.

For reference, the function was originally introduced in
commit 46b252d ("Added progressive rendering", 2018-04-20)

Also renamed ivar from `viewUpDirectionChangeSpeed` to `viewUpChangeSpeed`

…d()`

Since having the head-mounted display (HMD) connected may not always be
a good proxy to check if the initialization succeeded, we instead swith to
the dedicated `GetVRInitialized` function available since commit
Kitware/VTK@bddd94efd3 ("Improve OpenVR/OpenXR module and test and enable
OpenXR in CI", 2023-01-11)

Moreover, the determination of whether the event loop should run has been
refined by relying on the GetVRInitialized function as the primary criterion.
In the case of the OpenVR runtime, the use of GetHMD is retained through the
introduction of the `hmdConnected` internal variable for enhanced flexibility.

- Introduce the CMake option `SlicerVirtualReality_HAS_OPENVR_SUPPORT`,
  initialized to OFF on macOS.

- Introduce `vtkMRMLVirtualRealityConfigure.h`, a configurable header
  facilitating conditional compilation based on the presence of the macro
  `SlicerVirtualReality_HAS_OPENVR_SUPPORT`.

- Update `vtkVirtualRealityViewInteractorObserver::GetInteractorStyleDelegate`
  to dynamically return the current delegate based on the availability
  of OpenVR support.

- Ensure that when OpenVR support is disabled, proper linkage against
  the `VTK::RenderingVR` target is maintained, providing a backend-agnostic
  interface.

…tions.json`

- Add SlicerVirtualReality_HAS_OPENXR_SUPPORT CMake option

- Add OpenXR-SDK and vtkRenderingOpenXR external projects

- Add OpenXR specialized interactor style class for.

- Add OpenXR specialized interactor class. Thanks to the shared
  `vtkVirtualRealityComplexGestureRecognizer`, there is no duplicated code.

- Add OpenXR specialized interactor style class. Thanks to the shared
  `vtkVirtualRealityViewInteractorStyleDelegate`, there is no duplicated code.

- Update vtkSlicerVirtualRealityLogic::ComputeActionManifestPath support
  for `OpenXR`.

- Update `vtkMRMLVirtualRealityViewNode` adding `OpenXR` to `XRRuntimeType` enum

- Update `qMRMLVirtualRealityView::createRenderWindow` to instantiate `vtkOpenXR*` classes

- Update  `qMRMLVirtualRealityView::currentXRRuntime` to check for OpenXR