Move kicad_libraries to racklet-kicad-lib repo

[chiplet]

racklet-kicad-lib hosts the custom symbol and footprint libraries for the components used in racklet hardware prototypes. The symbols defined in kicad_libraries directory should be moved there.

[chiplet]

TODO:

• Move symbols to racklet-kicad-lib
• Merge racklet-kicad-lib/pull/6
• Update relevant designs by adding racklet-kicad-lib as a submodule to relevant designs and updating the symbols used.