Restore previous non-tracked camera pose on esc

[Wumpf]

Allow the user to revert to the previous camera pose whenever a 3d camera is tracked.

Screen.Recording.2023-02-05.at.20.23.12.mov

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
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• I've added a line to CHANGELOG.md (if this is a big enough change to warrant it)

[emilk]

Very nice!

It would be great if both this and the "click on camera" behavior was documented in HELP_TEXT_3D. We should strive to not have too many hidden features.

[Wumpf]

yeah this was mostly meant as a quick and dirty fix for Niko's recording woes which then got good enough to land :)
Considering this again I'd like to encapsulate state_3d's camera state a bit better because there is now a high risk all these different states get out of sync.
Also there is the matter of the somewhat odd "you need to hover this space view and then press Escape" which on one hand is weird and on the other hand totally necessary because otherwise we react on Esc in all sort of contexts. But I'm wondering if there is another way of expressing "this view has focus"