chore(tracing): extract app start to a standalone integration

[krystofwoldrich]

:loudspeaker: Type of change

• [ ] Bugfix
• [ ] New feature
• [x] Enhancement
• [x] Refactoring

:scroll: Description

:bulb: Motivation and Context

:green_heart: How did you test it?

:pencil: Checklist

• [ ] I reviewed submitted code
• [ ] I added tests to verify changes
• [ ] No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled
• [ ] All tests passing
• [ ] No breaking changes

:crystal_ball: Next steps

[github-actions[bot]]

Android (legacy) Performance metrics :rocket:

	Plain	With Sentry	Diff
Startup time	448.82 ms	519.66 ms	70.84 ms
Size	17.73 MiB	20.04 MiB	2.31 MiB

[github-actions[bot]]

iOS (legacy) Performance metrics :rocket:

	Plain	With Sentry	Diff
Startup time	1222.87 ms	1227.10 ms	4.23 ms
Size	2.36 MiB	3.05 MiB	706.54 KiB

[github-actions[bot]]

iOS (new) Performance metrics :rocket:

	Plain	With Sentry	Diff
Startup time	1237.00 ms	1231.53 ms	-5.47 ms
Size	2.92 MiB	3.61 MiB	707.68 KiB

[github-actions[bot]]

Android (new) Performance metrics :rocket:

	Plain	With Sentry	Diff
Startup time	344.73 ms	378.84 ms	34.11 ms
Size	7.15 MiB	8.19 MiB	1.04 MiB