No functional changes.
The `BeztMap` struct is used when sorting Keyframes during transformations
in the Graph Editor.
Things that were changed:
* Removed unneeded `newIndex`. This was just the index of the
`BeztMap` in the array, which we already have since we iterate with a for loop.
* Access the `BezTriple` array by index instead of pointer offsets.
This makes it a bit easier to see what's happening.
* Renamed struct members to clarify their use.
* Remove forward declaration of certain variables (e.g. loop counter vars)
Pull Request: https://projects.blender.org/blender/blender/pulls/119733
adef64db06