Move art's java_system_modules into a shared inner tree

These will be built using the toolchains of the respective inner tree.
This will eventually allow us to drop them from the module SDK (albeit
we still need to make them work for S/T builds)

Test: TH
Bug: 261476442
Change-Id: I43726a2a171d25ace90dc3ddc73e228ffadfb37c