Track property editor: enforce I cursor, hide while typing

[ronso0]

When I open the editor I sometimes see it changing the cursor to I but it reverts to regular pointer as soon as I move it.
Thing is the pointer gets in the way of editing.
Idk if this is a Qt bug (I'm on 6.2.3 with Ubuntu + X11 + xfce4)
or if we need to implement it manually.
FWIW it works as expected in the library editor delegates (except auto-hide of course)

• enforce I cursor in editor
• hide cursor while typing (restores I on mouse move) -> do we want it or is it too invasive?

TODO

• test on Windows 10/11. There's a comment in widget/knobeventhandler.h that says it didn't in earlier versions (in 2018), details somewhere here