feat: branch diff adjust icons for file status

[gerhardol]

Proposed changes

Modify the icons for the file status list when comparing branches with a common base, the info with feedback for where the files are changed: Unequal/B (second), A (first), Same (both changes the same).

Color is added to give some feedback of the change in addition to the (pixel) character: B (blue-violet), A (yellow) and same (green) (unequal was red already).
Some minor anti-aliasing too.

Also prepare the icons for dark mode.
Edit: also updated added/removed/copied/renamed (just modified first) (all submodule related are not changed, as before).

Related to #12111
This could be handled in that PR too, but the intention is that that PR in itself should have a minimal of changes to the light mode.

PHYs attribute has been removed with TweakPng

Screenshots

Before

Dark mode is not used, but the pixel char is hard to see with dark text

After

Slightly darker background than in the app

Test methodology

Visual

Test environment(s)

Win11

Merge strategy

I agree that the maintainer squash merge this PR (if the commit message is clear).

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✒️ I contribute this code under The Developer Certificate of Origin.

[mstv]

This seems to be an acceptable compromise.
But no anti-aliasing, please! I.e. only one color for each character ('A' and 'B' need to be changed).
The pHYs section needs to removed, e.g. using https://entropymine.com/jason/tweakpng. I could not find the other PNG optimizer tool.

[gerhardol]

This seems to be an acceptable compromise. But no anti-aliasing, please! I.e. only one color for each character ('A' and 'B' need to be changed). The pHYs section needs to removed, e.g. using https://entropymine.com/jason/tweakpng. I could not find the other PNG optimizer tool.

PHYs are removed already - will need to be removed again after updates...
The icons look slightly better with anti aliasing (may not be more readable) I can remove anti aliasing, will be easier to implement to the other icons then...

[mstv]

Perhaps, use some yellowish color for the "AA" in "renamed" icons.

[gerhardol]

The normal icon is OK, just branch compare that are kept black

Notice the incorrect length for the marking, in #12116 (as the tooltip is removed in that PR too, it is hard to see the original file name)

Wrong icon for renamed (also in master)