Implement metrics agent for built_test_suites

Implement the metrics agent for build_test_suites. This will report
metrics for optimization decisions and build/analysis times for the
build_test_suites script.

Test: atest build_test_suites_test
Bug: 372973116
Change-Id: I6b6b726b93de6ab3fbb49a95ebadd5338859fcaf