feat: Split up UIKit and App Init App Start Spans

[philipphofmann]

📜 Description

Split the UIKit and Application Init span into one span for UIKit Init and another for Application Init. The UIKit Init span ends when the users start the SentrySDK. We recommend that the SentrySDK is the first to call in the UIApplication.didFinishLaunching method because otherwise, users won't receive any potential crash reports for code running before our SDK. Therefore, we pick the start time of our SDK as when the UIApplicationDelegate.didFinishLaunching is called.

Docs PR getsentry/sentry-docs#8814.

Before

Now

💡 Motivation and Context

Fixes GH-3345

💚 How did you test it?

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Split up UIKit and App Init App Start Spans ([#3534](https://github.com/getsentry/sentry-cocoa/pull/3534))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against cc4f99d

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f74904f) 89.213% compared to head (b1c6c84) 89.234%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3534       +/-   ##
=============================================
+ Coverage   89.213%   89.234%   +0.020%     
=============================================
  Files          528       528               
  Lines        57620     57472      -148     
  Branches     20637     20334      -303     
=============================================
- Hits         51405     51285      -120     
- Misses        5185      5271       +86     
+ Partials      1030       916      -114     

Files	Coverage Δ
Sources/Sentry/SentryAppStartMeasurement.m	100.000% <100.000%> (ø)
Sources/Sentry/SentryAppStartTracker.m	97.619% <100.000%> (+0.014%)	⬆️
Sources/Sentry/SentryBuildAppStartSpans.m	95.384% <100.000%> (+0.384%)	⬆️
Sources/Sentry/SentrySDK.m	90.123% <100.000%> (+0.123%)	⬆️
...SentryProfilerTests/SentryProfilerSwiftTests.swift	97.855% <100.000%> (+0.086%)	⬆️
.../AppStartTracking/SentryAppStartTrackerTests.swift	98.500% <100.000%> (+0.007%)	⬆️
Tests/SentryTests/Protocol/TestData.swift	98.936% <100.000%> (+0.003%)	⬆️
Tests/SentryTests/SentrySDKTests.swift	97.500% <100.000%> (+0.047%)	⬆️
...ts/SentryTests/Transaction/SentryTracerTests.swift	98.869% <100.000%> (-0.005%)	⬇️

... and 86 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1230.18 ms	1251.83 ms	21.65 ms
Size	21.58 KiB	418.82 KiB	397.24 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
e681215	6240.94 ms	6254.36 ms	13.42 ms
4053ee9	1248.04 ms	1250.82 ms	2.78 ms
302ee8b	1194.02 ms	1223.34 ms	29.32 ms
25bcc50	1240.47 ms	1254.70 ms	14.23 ms
cce35c6	1228.88 ms	1241.14 ms	12.26 ms
7bb0873	1226.18 ms	1247.30 ms	21.12 ms
10ee2ce	1250.90 ms	1258.57 ms	7.67 ms
7bc3c0d	1212.35 ms	1228.94 ms	16.59 ms
f587451	1271.63 ms	1275.90 ms	4.27 ms
d61b939	1238.61 ms	1240.08 ms	1.47 ms

App size

Revision	Plain	With Sentry	Diff
e681215	20.76 KiB	431.91 KiB	411.15 KiB
4053ee9	20.76 KiB	435.22 KiB	414.46 KiB
302ee8b	20.76 KiB	419.62 KiB	398.87 KiB
25bcc50	20.76 KiB	427.22 KiB	406.46 KiB
cce35c6	20.76 KiB	425.80 KiB	405.04 KiB
7bb0873	22.85 KiB	407.09 KiB	384.24 KiB
10ee2ce	20.76 KiB	427.77 KiB	407.00 KiB
7bc3c0d	20.76 KiB	427.35 KiB	406.59 KiB
f587451	20.76 KiB	435.25 KiB	414.49 KiB
d61b939	22.85 KiB	407.63 KiB	384.78 KiB

Previous results on branch: feat/did-finish-launching-span

Startup times

Revision	Plain	With Sentry	Diff
443cce2	1203.04 ms	1220.21 ms	17.17 ms
baaa45f	1214.87 ms	1245.02 ms	30.15 ms

App size

Revision	Plain	With Sentry	Diff
443cce2	21.58 KiB	418.82 KiB	397.24 KiB
baaa45f	21.58 KiB	418.82 KiB	397.24 KiB

[brustolin]

LGTM