[Icons] Render a badge/sticker sheet for every shipped theme

The PR showed one theme's badge and sticker sheets, which cannot show that the
filled treatments read on every palette. Each shipped theme and scheme now
gets its own sheet: both semantic families, three glyphs, as line glyphs,
stickers and badges, at 16 and 24 px, on the window and button surfaces the
contrast is measured against, with the disabled fallback under each family.

The generator lives in its own test file so the preview work does not have to
move the branches above it.

tests/theme_migration/CMakeLists.txt

@@ -17,6 +17,7 @@ cockatrice_add_test(
   theme_migration_test.cpp
   theme_icon_render_test.cpp
   icon_tint_preview_test.cpp
+  icon_treatment_preview_test.cpp
   LIBS
   libcockatrice_settings
   libcockatrice_network