Rework bitmap cache and enable it

common/bitmap_base.cpp

common/dialogs/panel_image_editor.cpp

common/gal/opengl/opengl_gal.cpp

eeschema/sch_plugins/kicad/sch_sexpr_parser.cpp

eeschema/sch_plugins/legacy/sch_legacy_plugin.cpp

include/bitmap_base.h

pcbnew/plugins/kicad/pcb_parser.cpp