Add experimental Bazel mode support for on-device tests

Add an experimental Atest flag and supporting logic to run TradeFed on-device tests with Bazel mode. This feature is disabled by default and required passing the `--experimental-device-driven-test` flag on the Atest command line.

Test: atest-src atest_unittests --host --bazel-mode
Test: atest-src HelloWorldTests --bazel-mode --experimental-device-driven-test
Bug: 220263783
Change-Id: Ifa074e0a2ef725bdd3228926e4af72492f5907c7
5 files changed