[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/ready_start.svg

@@ -1,81 +1,3 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<!-- Created with Inkscape (http://www.inkscape.org/) -->
-
-<svg
-   xmlns:dc="http://purl.org/dc/elements/1.1/"
-   xmlns:cc="http://creativecommons.org/ns#"
-   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
-   xmlns:svg="http://www.w3.org/2000/svg"
-   xmlns="http://www.w3.org/2000/svg"
-   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
-   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
-   width="500"
-   height="500"
-   id="svg2"
-   version="1.1"
-   inkscape:version="0.48.5 r10040"
-   sodipodi:docname="icon_ready_start.svg">
-  <defs
-     id="defs4">
-    <inkscape:perspective
-       sodipodi:type="inkscape:persp3d"
-       inkscape:vp_x="0 : 526.18109 : 1"
-       inkscape:vp_y="0 : 1000 : 0"
-       inkscape:vp_z="744.09448 : 526.18109 : 1"
-       inkscape:persp3d-origin="372.04724 : 350.78739 : 1"
-       id="perspective10" />
-  </defs>
-  <sodipodi:namedview
-     id="base"
-     pagecolor="#ffffff"
-     bordercolor="#666666"
-     borderopacity="1.0"
-     inkscape:pageopacity="0.0"
-     inkscape:pageshadow="2"
-     inkscape:zoom="1.4339754"
-     inkscape:cx="281.46845"
-     inkscape:cy="299.09369"
-     inkscape:document-units="px"
-     inkscape:current-layer="layer1"
-     showgrid="false"
-     inkscape:window-width="1600"
-     inkscape:window-height="1178"
-     inkscape:window-x="1912"
-     inkscape:window-y="-8"
-     inkscape:window-maximized="1"
-     showguides="true"
-     inkscape:guide-bbox="true" />
-  <metadata
-     id="metadata7">
-    <rdf:RDF>
-      <cc:Work
-         rdf:about="">
-        <dc:format>image/svg+xml</dc:format>
-        <dc:type
-           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
-        <dc:title />
-      </cc:Work>
-    </rdf:RDF>
-  </metadata>
-  <g
-     inkscape:label="Ebene 1"
-     inkscape:groupmode="layer"
-     id="layer1"
-     transform="translate(0,-552.36218)">
-    <path
-       sodipodi:type="arc"
-       style="fill:#0dc700;fill-opacity:1;fill-rule:nonzero;stroke:#000000;stroke-opacity:1;stroke-width:5.46761148;stroke-miterlimit:4;stroke-dasharray:none"
-       id="path2984"
-       sodipodi:cx="-137.08441"
-       sodipodi:cy="104.52625"
-       sodipodi:rx="182.45049"
-       sodipodi:ry="182.45049"
-       d="m 45.366074,104.52625 c 0,100.76462 -81.685865,182.45049 -182.450484,182.45049 -100.76462,0 -182.45049,-81.68587 -182.45049,-182.45049 0,-100.7646178 81.68587,-182.450482 182.45049,-182.450482 100.764619,0 182.450484,81.6858642 182.450484,182.450482 z"
-       transform="matrix(1.3351351,0,0,1.3351351,434.51202,663.29215)" />
-    <path
-       style="fill:#ffffff;fill-opacity:1;fill-rule:nonzero;stroke:none"
-       d="m 375.18246,681.4936 -180.66822,156.20036 -62.11391,-71.84189 -57.207882,49.50276 110.831342,128.16069 0.15088,-0.11694 0.7485,0.87896 237.72517,-205.58619 -49.46594,-57.19777 z"
-       id="rect3754"
-       inkscape:connector-curvature="0" />
-  </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">
+<path d="M4 12l5 5L20 6"/>
 </svg>