Remove suffix based stub matching logic

This change prevents non-stub modules with stub suffix from being
determined as the stub module, and instead makes the check more robust
by determining the condition based on the user-hidden
`Stub_contributing_api` property, which is only set for the stub
submodules generated by `java_sdk_library`.

Test: m nothing --no-skip-soong-tests
Bug: 361179822
Change-Id: I28a599c5b4fe1e8460e60580c0535aaf19e39ba3