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.
Also removes EditToolSelectionFilter which was misused in more places
than it was used correctly. The original point of the client filter
was to move the logic to the point of use, which the
EditToolSelectionFilter sort of obviated anyway.
Fixes https://gitlab.com/kicad/code/kicad/issues/6751
Jeff Young
Marek Roszko
Jon Evans