Specify Is_stubs_module property in top level sdk library

java_sdk_library's "magic" will always resolve to stubs when either of
the following conditions are met:
- the module sets `api_only` property to "true": this signifies that
  the module does not create an implementation library, thus the "magic"
  always returns stubs
- the module sets `default_to_stubs` property set to "true": this
  signifies that the reverse dependencies outside of the same apex will
  always get the stubs, even when the rdep does not specify the
  sdk_version.

This change utilize this information and mark the top level sdk_library
as a stubs module when any of the above conditions are met, in order to
minimize the false positives in container violation errors.

Test: Run container enforcement and observe results
Bug: 354029496
Change-Id: I04b52c5662f635ab1837eb33a39f187ae8998238