Cargo2Android: add rdep tests to TEST_MAPPING

This is important because:
1. Some crates do not have their own tests enabled in presubmit.
2. As much as possible, we try to stick with one version of each
   crate. This often results in using different versions of
   dependencies than a crate has specified in its Cargo.toml.

Ensuring that a crate's tests continue to pass when its dependencies
are upgraded improves our confidence that the update is safe.

The underlying implementation uses the new Bazel queryview
to query modules and reverse dependencies.

Bug: 168167373
Test: Run cargo2android.py on a number of crates including rusqlite,
scopeguard, lock_api.

Change-Id: Id24f2d3267cf8d5e0369ece2442f8971d4ab1343
3 files changed