2023-12-01

Add time_to_first_test_discovery

Summary: This timing information gives an insight of how long it takes to finish building the first test binary when 'buck2 test' is executed. It captures the first test discovery time because it occurs earlier than all the test execution.

Reviewed By: iguridi

Differential Revision: D51673956

fbshipit-source-id: 82ee4c9da2a5971ab805768b0af5595367a1228b