[WIP] feat: update icons

[fdrgsp]

Using pymmcore-gui on Windows, I noticed that the toolbar icons looked quite thin, the mouse hovering was not very visible and the toggle state on/of was not clear.

In this PR I tried to modify the look/behavior of the icon. The color I choose are simply to make the change clear, but we can discuss about the palette.

Screen.Recording.2025-02-16.at.11.19.50.AM.mov

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 64.71%. Comparing base (3995dad) to head (ca9c513).

Files with missing lines	Patch %	Lines
src/pymmcore_gui/actions/core_actions.py	20.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
- Coverage   64.79%   64.71%   -0.08%     
==========================================
  Files          18       18              
  Lines        1156     1162       +6     
==========================================
+ Hits          749      752       +3     
- Misses        407      410       +3     

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[tlambert03]

yeah... anything that uses setStyleSheet is something I'm going to have difficulty with, except in specific cases (such as something like #39 where it never needs to blend in to its surroundings)

I'd like to have some sort of theme idea in place (#4) before we start picking colors that look good ad hoc

[tlambert03]

I was starting to look a bit at themeing in https://github.com/tlambert03/pymmcore-gui/tree/theme (diff)

[gselzer]

This may be unrelated, but the icons can be nearly invisible on dark-themed Windows (especially if there's any glare/dust on the monitor):

[tlambert03]

Not unrelated, but definitely related to #4

We need a global awareness of theme, and it should include colors of icons, backgrounds, etc

[marktsuchida]

@gselzer and I found that if you switch the Accent Color in Windows's Settings > Personalization > Colors, then Qt will use that color for highlighting the buttons.