fix(session-replay): improve multi-threading of session replay processing

[philprime]

📜 Description

• Changes the priorities of the background queues of session replay.
• Refactors the async dispatch handling of session replay.

💡 Motivation and Context

Some of the methods of the session replay video processing are dispatched to a low priority background queue, which then dispatches additional AV work on another dispatch queue.

The current implementation does not respect queue priorities and can cause thread starvation, because the processing queue and the work queue are either on the same priority, or the work queue is on a lower priority.

In the worst case, the processing queue is blocked and waits for the work queue, but the work queue has a lower priority than the processing queue and is awaiting execution on the main thread.

This is what the thread inversion warning is showing.

Closes #4730

💚 How did you test it?

Manual testing.

📝 Checklist

You have to check all boxes before merging:

• 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.
• I updated the wizard 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.

[github-actions]

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

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

- improve multi-threading of session replay processing ([#5018](https://github.com/getsentry/sentry-cocoa/pull/5018))

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 a27d74d

[philprime]

I would appreciate feedback if you asee any issues with this approach for synchronizing the async call

[philprime]

Moved this setup to the SentryDispatchQueueWrapper to make it replaceable

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1230.29 ms	1241.67 ms	11.38 ms
Size	22.30 KiB	836.54 KiB	814.24 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
4597906	1228.37 ms	1242.29 ms	13.92 ms
9d61bea	1243.88 ms	1254.36 ms	10.48 ms
6001822	1234.49 ms	1265.20 ms	30.71 ms
706c41f	1231.00 ms	1248.52 ms	17.52 ms
9ef729b	1228.79 ms	1245.36 ms	16.57 ms
7bc3c0d	1212.35 ms	1228.94 ms	16.59 ms
80da9d1	1193.76 ms	1211.83 ms	18.08 ms
b9b0f0a	1251.45 ms	1257.86 ms	6.41 ms
75f7fc8	1239.31 ms	1266.12 ms	26.82 ms
0589699	1233.49 ms	1249.09 ms	15.60 ms

App size

Revision	Plain	With Sentry	Diff
4597906	21.58 KiB	678.19 KiB	656.61 KiB
9d61bea	20.76 KiB	436.29 KiB	415.53 KiB
6001822	22.85 KiB	410.98 KiB	388.13 KiB
706c41f	21.58 KiB	699.25 KiB	677.67 KiB
9ef729b	20.76 KiB	432.88 KiB	412.12 KiB
7bc3c0d	20.76 KiB	427.35 KiB	406.59 KiB
80da9d1	21.58 KiB	418.45 KiB	396.86 KiB
b9b0f0a	20.76 KiB	434.94 KiB	414.18 KiB
75f7fc8	21.58 KiB	704.23 KiB	682.65 KiB
0589699	21.58 KiB	656.60 KiB	635.02 KiB

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 260 lines in your changes missing coverage. Please review.

Project coverage is 8.861%. Comparing base (ba5cc98) to head (a27d74d).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...egrations/SessionReplay/SentryOnDemandReplay.swift	0.000%	183 Missing ⚠️
Sources/Sentry/SentrySessionReplayIntegration.m	0.000%	51 Missing ⚠️
...tegrations/SessionReplay/SentrySessionReplay.swift	0.000%	22 Missing ⚠️
Sources/Sentry/SentryDispatchQueueWrapper.m	0.000%	4 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (ba5cc98) and HEAD (a27d74d). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (ba5cc98)	HEAD (a27d74d)
	4	1

Additional details and impacted files

@@              Coverage Diff              @@
##              main    #5018        +/-   ##
=============================================
- Coverage   92.705%   8.861%   -83.844%     
=============================================
  Files          672      358       -314     
  Lines        82202    25570     -56632     
  Branches     29841       94     -29747     
=============================================
- Hits         76206     2266     -73940     
- Misses        5899    23304     +17405     
+ Partials        97        0        -97     

Files with missing lines	Coverage Δ
...rations/SessionReplay/SentryReplayVideoMaker.swift	0.000% <ø> (-100.000%)	⬇️
Sources/Sentry/SentryDispatchQueueWrapper.m	52.542% <0.000%> (-47.458%)	⬇️
...tegrations/SessionReplay/SentrySessionReplay.swift	0.000% <0.000%> (-97.657%)	⬇️
Sources/Sentry/SentrySessionReplayIntegration.m	0.000% <0.000%> (-88.611%)	⬇️
...egrations/SessionReplay/SentryOnDemandReplay.swift	0.000% <0.000%> (-94.175%)	⬇️

... and 659 files with indirect coverage changes

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