This adds versioning code that replaces any timeline with a
dopesheet where the footer is shown, AND it removes the
timeline from the menu options.
If the area is too small to show both, the footer and the
header then only the footer is shown.
This assumes that users created the small timeline
just for the playback controls
Any uses of `SACTCONT_TIMELINE` (except for versioning) have been removed.
part of #145577
Pull Request: https://projects.blender.org/blender/blender/pulls/147058
2ae953d7f5