This commit changes the keying code to deselect keyframes when inserting new keys.
This has been discussed in the Animation & Rigging module meeting [1].
There is also an RCS post about that [2].
Doing this brings key creation in line with object creation,
where only the newly created object is selected.
There has been a previous attempt [3] to do a similar thing.
### Changes
When inserting keys by pressing `I` in the viewport or choosing a keying set,
all keys of the `Action` get deselected before inserting new keys.
New keys are selected by default.
Python RNA functions are **NOT** affected, meaning addons using
those functions will not deselect any keys by default.
The developer has to choose to do so.
To make that easier, there is a new RNA function on the action
`deselect_keys`
[1]: https://devtalk.blender.org/t/2024-05-02-animation-rigging-module-meeting/34493#patches-review-decision-time-5
[2]: https://blender.community/c/rightclickselect/K0hbbc
[3]: https://archive.blender.org/developer/D11623
Pull Request: https://projects.blender.org/blender/blender/pulls/121908
6ef77a0d22