Default implementation of drag-scroll

[eynsai]

Description

This PR adds a default implementation of drag-scroll to QMK. High-resolution drag-scroll can potentially be much more complicated than conventional drag-scroll, making a default implementation useful. This PR cannot be merged independently. It strictly depends on PR 24422 being merged. Additionally, it depends on PR 24423 and PR 24424 - to the best of my knowledge it'll work without 24423 and 24424, but the value proposition of this PR will be substantially reduced without them.

Code is feature-complete, documentation is WIP.

Key features include:

• Automatic scaling based on whether high resolution scrolling is on or not
• Rate throttling (independently of the throttling applied to all pointing device tasks)
• Sliding-window smoothing
• Rounding error accumulation
• X/Y axis snapping
• Acceleration (velocity transfer curve)
• Support for POINTING_DEVICE_COMBINED

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).