Property editor: Hide header and enable resizing on all cells.

[PaddleStroke]

Fixes #11794

Hide headers of property view as they are self explanatory:

And enable resizing on all cells (as before you could resize only on headers, which was a problem if you hide headers).

[MisterMakerNL]

nice! Tnx for your work!

[maxwxyz]

@PaddleStroke
now only this is floating in mid air:

Or is this from the theme @obelisk79

[MisterMakerNL]

With default stylesheets there is an issue that the background of the properties panel is not see true.
The issue is from the overlay system I have not find a way to target the text with no background directly and just targeted the properties panel itself. So to prevent unreadable text I decided it is better to have readable text then no panel there.
This issue is also without stylesheets:

[maxwxyz]

@PaddleStroke not sure if related to this PR but I have duplicate panel names when using a multiple screen setup with two different DPIs on the screen:

In general 0.22dev is a step back to the stable 0.21.2 regarding UI scaling and display #13118

[maxwxyz]

added #13349 maybe you know a quick fix @PaddleStroke

[PaddleStroke]

I do not think the issue you describe has anything to do with this PR.