[Icons] Migrate UI glyphs to palette-token SVGs

Runtime inversion is not a theming system: it rotates hue, breaks duotone art
and mishandles alpha, and a QPixmap snapshot cannot follow a palette change.
Redraw the top-level UI glyph set on a 24x24 grid with `currentColor` as the
paint token, drop Inkscape/Sodipodi cruft, and delete the icons whose metaphor
was duplicated (cogwheel/gear -> settings, scale_balanced -> scales,
update.png -> reload).

Load the glyphs through `loadThemedIcon` so the engine resolves the token from
the palette on every request, and let `themePixmap` use the same resolution for
one-shot pixmaps. `loadColorAdjustedPixmap` is gone; every caller now keeps a
QIcon, which `SettingsButtonWidget::setButtonIcon` accepts instead of a QPixmap.

Content art (mana, counters, countries) keeps its authored colors.

Add a render test covering aspect ratio, palette flips, icon modes and
high-DPI pixmaps.

cockatrice/resources/icons/share.svg

@@ -1,25 +1,7 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<!-- Uploaded to: SVG Repo, www.svgrepo.com, Generator: SVG Repo Mixer Tools -->
-
-<svg height="800"
-     width="800"
-     version="1.1"
-     id="_x32_"
-     viewBox="0 0 512 512"
-     xml:space="preserve"
-     xmlns="http://www.w3.org/2000/svg"
-     xmlns:svg="http://www.w3.org/2000/svg">
-    <defs id="defs1"/>
-    <style type="text/css"
-           id="style1">
-	.st0{fill:#64C0FF;stroke:black;stroke-width:3;stroke-miterlimit:4;stroke-opacity:1}
-</style>
-    <g id="g1"
-       transform="matrix(0.87097097,0,0,1.0008579,38.609049,-0.21963163)"
-       style="stroke-width:3.42738;stroke-dasharray:none">
-	<path class="st0"
-          d="M 512,255.995 277.045,65.394 v 103.574 c -17.255,0 -36.408,0 -57.542,0 -208.59,0 -249.35,153.44 -201.394,266.128 9.586,-103.098 142.053,-100.701 237.358,-100.701 7.247,0 14.446,0 21.578,0 v 112.211 z"
-          id="path1"
-          style="stroke-width:20;stroke:#000000;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none"/>
-</g>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+<circle cx="6" cy="12" r="2.5"/>
+  <circle cx="18" cy="6" r="2.5"/>
+  <circle cx="18" cy="18" r="2.5"/>
+  <path d="M8.2 10.8l7.6-3.6"/>
+  <path d="M8.2 13.2l7.6 3.6"/>
 </svg>