Android: Add a way to prepare traces without running tests Example: % out/Android/angle_trace_tests --gtest_filter='*gacha_life' --prepare-only ... Prepared traces: {'gacha_life'} Can be used as a setup for running restricted_trace_perf.py Bug: b/292249127 Change-Id: I901c086a19e1d182c64ec4150ced98c198e21c4d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4711826 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Roman Lavrov <romanl@google.com>