[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/reload.svg

@@ -1,7 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
-<svg version="1.1" xmlns="http://www.w3.org/2000/svg" x="0px" y="0px"
-     viewBox="0 0 1000 1000" enable-background="new 0 0 1000 1000" xml:space="preserve">
-<metadata> Svg Vector Icons : http://www.onlinewebfonts.com/icon </metadata>
-    <g><path d="M586.9,373.6l95.6-84.4c-49.6-39.2-129.4-79.1-198.2-79.1c-134.9,0-248.2,90.5-280.2,212.8L10.6,374.5C64.4,168.3,255.2,15.8,482.5,15.8c126.7,0,258.8,63.7,345.4,141.4l90.8-80.1L990,479.6L586.9,373.6z M317.5,710.8c49.6,39.2,129.4,79.1,198.2,79.1c134.9,0,248.2-90.5,280.2-212.8l193.5,48.5c-53.7,206.2-244.6,358.7-471.9,358.7c-126.7,0-258.8-63.7-345.4-141.4l-90.8,80.1L10,520.4l403.1,106L317.5,710.8z"/></g>
-</svg>
+<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">
+<path d="M20 12a8 8 0 1 1-2.3-5.7"/>
+  <path d="M20 4v5h-5"/>
+</svg>