bp2build for java libraries using xsd_config srcs

In Soong, java libraries can use src files generated from xsd_config. In
Bazel, instead of providing srcs, java_xsd_config_library will provide a
jar. Update bp2build so that all src references to xsd_config modules in
srcs get routed to deps and exports attributes

This CL creates an interface in build/soong/android to get around a
circular dependency issue. The bp2build logic needs to exist in
soong-java, but soong-java does have soong-xsdc in its package path. Use
the interface and type assertions to special case xsd_config references

Bug: 211678537
Test: bp2build test in sibling CL in system/tools/xsdc
Change-Id: Ida924bb20b1fd7eb8beeef950b070d37a9c6f3b5