turn GeoAxis into a block and fix projection

[SimonDanisch]

Needs: MakieOrg/Makie.jl#2645

This changes the axis to use a manual Makie.@Block macro, to re-create something similar to Makie.Axis, without creating a whole Makie.Axis.

Enables:

• chose axis=(; type=GeoAxis) and pass all other axis attributes like that:

  • lines(GeoMakie.coastlines(); axis=(; type=GeoAxis))

• Plots now can pass source=source_data_projection , to allow for different input source projections

  • lines!(axis, ..., source="+proj=longlat +datum=WGS84")
  • GeoAxis still has a default source_projection = "+proj=longlat +datum=WGS84" and target_projection = "+proj=eqearth"
  • we can overload create_transform(dest::String, source::String) for other projection types then Proj + strings

• intercepts poly call to create triangulation after projection, removing incorrect triangulations form distorting projections

• the GeoAxis now doesn't have it's own transform_func, and just works on "normal" 2d data, getting rid of all the limit problems (instead, the plot data gets it's own transformation and get transformed before plotting)

  • with this zooming + panning etc works much better

TODOs

• add better gridlines + ticks
• tests
• apply @gaelforget split method in apply_transform ... But I think we'll need to make the split function projection aware for that first?
• add attributes like title

Stretch goal

• refactor Makie Axis code to be better re-usable (I had to copy quite a few methods out of Makie/makielayout/blocks/axis.jl, since it was just almost working, but had a few tiny things that were different, or simply methods that were restricted to ::Axis

[asinghvi17]

Current TODO list is:

• Add title and subtitle capabilities
• Add protrusions back in
• Add automatic limit finding for projections (aka the dumb and brute force way) back in
• Figure out a solution to show axes where the limits in long, lat space are not a rectangle, i.e., orthographic plots with the pole at an angle