Add dependencies for source-generated crates

When using SourceProviders, the dependency tree does not include
directly the source variant, only the built variant. For instance:

  liba --> libbingena_rlib --> libbingena_source

However, libbindgena_rlib did not have a source associated with the
module, and was therefore not added as a dependency. Modify the logic so
that a SourceProvider library will find the right variant and always
have a source defined.

Adds display_name fields to the crate description to ease debugging.

Test: rust-analyzer analysis-stats .
Bug: 174158339
Change-Id: Id65708d57cd176f7e1da353f4a5f7ad65b003090