Remove ExpandSourcesSubDir and ModuleSrcPath.WithSubDir

Replace ExpandSourcesSubDir with ExpandSources plus
PathsWithModuleSrcSubDir, which loops over the paths and uses
Join to create paths relative to subdir on any results that
are ModuleSrcPaths.

Test: All soong tests
Change-Id: I11a7face88641e2c26ccdca0a3117d5c38ab588e