test(android): Add Jetpack Macrobenchmark for SDK init performance (JAVA-604) (#5680)

Add sentry-uitest-android-macrobenchmark, a cold-start Macrobenchmark
targeting sentry-samples-android. It reports timeToInitialDisplay from
framework trace events, requiring no trace markers in the SDK or app.
Per-iteration perfetto traces are saved for deeper analysis.

CompilationMode.Full pins ART AOT; iterations are capped at 12 because
back-to-back cold starts thermally throttle after ~14 iterations. To
A/B an SDK change, interleave per-variant rounds so thermal drift does
not systematically penalize the second variant (see README).

Verified on a Galaxy A55 (Android 16): TTID median 514.5ms over 12
iterations. Requires androidx.benchmark 1.4.1; 1.3.4 fails to confirm
activity launches on API 36.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>