[Startup Tracing][Telemetry] Support customizable trace options in TBM
This CL updates Telemetry to support customizable Chrome trace options. This will be needed by startup tracing. Currently, only the record mode and systrace are supported. We can add other trace options if we need them later.
Startup tracing design doc:
https://docs.google.com/document/d/1yRCXhrQ-0rsfUgNHt9T4YdnmJYrXKN6aK56Ozk3kPVc/edit#heading=h.7suon55jg9u4
BUG=317481, 482098
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect
Review URL: https://codereview.chromium.org/
1215533002
Cr-Commit-Position: refs/heads/master@{#337862}