fix: Don't use main thread for app hang screenshot and view hierarchy

[brustolin]

📜 Description

During an app hang event, we attempt to capture a screenshot and view hierarchy in the main thread. However, the main thread is blocked, so the event must wait for the main thread to be freed, a situation that may never occur.

💡 Motivation and Context

Close #3220

💚 How did you test it?

Unit Test

📝 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]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1226.92 ms	1249.82 ms	22.90 ms
Size	21.58 KiB	418.70 KiB	397.11 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
1437c68	1244.86 ms	1254.18 ms	9.32 ms
7c5d161	1224.38 ms	1249.66 ms	25.28 ms
6001822	1202.61 ms	1213.50 ms	10.89 ms
257c2a9	1239.52 ms	1251.08 ms	11.56 ms
2af280d	1246.22 ms	1253.10 ms	6.88 ms
ecd9ecd	1191.76 ms	1216.92 ms	25.16 ms
ad7cec6	1203.22 ms	1224.74 ms	21.52 ms
01a28a9	1237.78 ms	1259.04 ms	21.27 ms
a176fc4	1226.24 ms	1247.50 ms	21.26 ms
98752f3	1240.61 ms	1259.80 ms	19.18 ms

App size

Revision	Plain	With Sentry	Diff
1437c68	22.85 KiB	410.96 KiB	388.11 KiB
7c5d161	20.76 KiB	414.44 KiB	393.68 KiB
6001822	22.85 KiB	410.98 KiB	388.13 KiB
257c2a9	20.76 KiB	401.36 KiB	380.60 KiB
2af280d	20.76 KiB	435.22 KiB	414.46 KiB
ecd9ecd	20.76 KiB	420.23 KiB	399.47 KiB
ad7cec6	20.76 KiB	427.32 KiB	406.55 KiB
01a28a9	22.85 KiB	405.39 KiB	382.54 KiB
a176fc4	22.84 KiB	403.24 KiB	380.39 KiB
98752f3	20.76 KiB	435.09 KiB	414.33 KiB

Previous results on branch: fix/screenshot-anr

Startup times

Revision	Plain	With Sentry	Diff
0a8b53c	1204.04 ms	1214.56 ms	10.52 ms
5d91312	1199.92 ms	1211.47 ms	11.55 ms
0f7cf35	1222.74 ms	1244.75 ms	22.01 ms

App size

Revision	Plain	With Sentry	Diff
0a8b53c	21.58 KiB	418.49 KiB	396.91 KiB
5d91312	21.58 KiB	419.20 KiB	397.61 KiB
0f7cf35	21.58 KiB	419.16 KiB	397.57 KiB

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (1c96132) 89.289% compared to head (78d91d8) 89.327%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3547       +/-   ##
=============================================
+ Coverage   89.289%   89.327%   +0.037%     
=============================================
  Files          529       529               
  Lines        57737     57979      +242     
  Branches     20412     20740      +328     
=============================================
+ Hits         51553     51791      +238     
  Misses        5276      5276               
- Partials       908       912        +4     

Files	Coverage Δ
Sources/Sentry/SentryANRTrackingIntegration.m	95.918% <100.000%> (ø)
Sources/Sentry/SentryEvent.m	98.518% <100.000%> (+0.045%)	⬆️
Sources/Sentry/SentryScreenshotIntegration.m	91.836% <100.000%> (+1.139%)	⬆️
Sources/Sentry/SentryViewHierarchy.m	98.979% <100.000%> (-0.011%)	⬇️
Sources/Sentry/SentryViewHierarchyIntegration.m	100.000% <100.000%> (ø)
...ations/ANR/SentryANRTrackingIntegrationTests.swift	94.339% <100.000%> (+1.436%)	⬆️
.../Screenshot/SentryScreenshotIntegrationTests.swift	99.382% <100.000%> (+0.091%)	⬆️
...Integrations/Screenshot/TestSentryScreenShot.swift	100.000% <100.000%> (ø)
...ierarchy/SentryViewHierarchyIntegrationTests.swift	99.159% <100.000%> (+0.190%)	⬆️
...ations/ViewHierarchy/TestSentryViewHierarchy.swift	100.000% <100.000%> (ø)
... and 4 more

... and 73 files with indirect coverage changes

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[philipphofmann]

Thanks for doing this. A couple of comments.

[philipphofmann]

Almost, LGTM.

[philipphofmann]

LGTM, thanks @brustolin 💪

[philipphofmann]

Again, LGTM.