Bitmaps are now identified by an enum class instead of by pointers.
Bitmap loading and caching is now handled by a class in common, and
we no longer compile most bitmaps into the binary, so there is no
longer a bitmaps static library.
Instead, bitmaps are archived to a .tar.gz file which is installed
in ${KICAD_DATA}/resources/images.tar.gz
The source PNGs are checked in to Git as the original CPP files were,
so that people can build without the required dependencies to convert
SVGs to PNGs.
Initial support is also added for dark theme icons, although this
is not yet exposed in the GUI.
Stubs are present for multi-resolution image resources, but this is
not fully-baked yet and could use some refinement.
We auto-size them in the code and doing both produces nothing but a
mess.
Also improves the auto-sizing for the layers drop-down (particularly
needed for the new, somewhat longer, layer names.
Fixes https://gitlab.com/kicad/code/kicad/issues/7671
Versions specific variables that may point to objects that change
through versions, allowing multiple KiCad versions to operate correctly
(even on MSW) on the same machine.