startop: Parse camera metrics from logcat for app_startup_runner

Parse ACTIVITY_FIRST_PREVIEW_FRAME_RECEIVED_ms,ACTIVITY_FIRST_PREVIEW_FRAME_RENDERED_ms
from logcat when running Camera app.

Also updates the scripts to support multiple metrics output (previously
only one allowed). Adding future per-app metrics is also possible by
just adding 1 file with 1 function call with a regex pattern.

Bug: 132649131
Change-Id: Ibfc620bb156f733b69faa7654b06ef35f1a34de3