Fixed AnimationTrackEditor redraw/deselect timing and some refactoring

[TokageItLab]

Fixed some weird redraw timings and most of errors by key editing.

Desktop.2022.08.29.-.11.18.15.01.mp4

In some edit commands, deselection and redraw were missing, causing errors in Undo/Redo during key selection. Also, there were many duplicates of the code for redraw, so it is refactored by making it a function.

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Additional fixes:

Follow up #64678, track key times are stored as double values, but if it store double value directly, the baked animation key finding was failing because Animation::track_find_key() comparisons are too strict. Fixed it by making baked keys in real_t time.¹

Some little fixes such as following up #64951 (renamed internal variables to more appropriate).

Footnotes

1. Also, it seems to be that the glTF animation times are baked as real_t in GLTFDocument::_serialize_animations(). If you want to store double values directly, we need to use Math::is_equal_approx() in Animation::track_find_key() ↩

[akien-mga]

Thanks!