F2 allows renaming lots of different types of active items, and now it
also works for markers.
Before, Ctrl+M was used, and it's context-sensitive: you often get
"Mirror Keys" instead, when your cursor isn't on the markers region, and
that operator has nothing to do with either renaming or markers.
**What this commit does:**
- Replace Ctrl+M shortcut with F2.
- Adds the `TOPBAR_PT_name_marker` panel which is implemented similar
to the global rename panel. This having to press enter twice to
confirm or escape twice to cancel, which would happen if the
`marker.rename` operator was called directly.
- Replace usages of `marker.rename` in the UI with `wm.call_panel`.
- To make the Industry Compatible keymap consistent with Blender
Default, the rename shortcut only works when hovering the markers
area.
Reviewed By: ChrisLend, sybren
Differential Revision: https://developer.blender.org/D12298
d6e7241237