Generate TEST_MAPPING for test modules in .bp file

* Share srcs in rust_defaults if len(srcs) is 1.

Test: regenerate .bp and TEST_MAPPING files in external/rust/crates
Test: make
Test: atest -c  --include-subdirs external/rust/crates
Bug: 161259631
Change-Id: I22a1d567ccabcd945e4cac870049ac3ce7a3049a
1 file changed