Blender Git Loki

UI: Theme refresh for Blender v3.0

{F11548100, size=full}

To celebrate the beginning of a new series, it feels like the right time to
give the theme a fresh look while improving on what already works.

The aim of this refresh is to keep a familiar look but with polishing touches
here and there. Like new paint on the walls of your well known house.

The theme for Blender 2.8 was well received but presented a few flaws.

* Transparency on menus and tooltips reduce readability
* Mismatch on certain colors, especially outlines of connected widgets
* Active/open menus highlight was not prominent enough
* Header background mismatch in some editors

At the same time we can make use of new features in 3.0:

* Make panels look like panels again (like in v2.3!)
* Make use of roundness in more widgets
* Since nodes are no longer hard-coded to be transparent, tweak opacity and saturation
* Tweak colors for the new dot grid

This update does not include:

* Meshes in edit mode to match greenish object-data color. This needs tweaks in the code to improve contrast.
* A copy of the Blender 2.8x legacy theme. This could be added to the community themes (shouldn't cost much maintenance, I hope)

There will be certainly small tweaks to do here and there, I've been working using this theme
for months but there can be areas that are missing update. The overall style is presented here.

This commit bumps the file subversion.

Reviewed By: #user_interface, Severin

Differential Revision: https://developer.blender.org/D13008