fix: Race condition in SentryApplication and Swift implementation

[noahsmartin]

SentryApplication was doing 2 things. It was wrapping UI/NSApplication methods for unit testing purposes, and it was attempting to provide background thread safe access to isActive. I say attempting because it used Notification Center to listen for foreground/background and change a state var, but didn't have any kind of locking. So it was prone to a data race where the main thread would write to it through the notification at the same time a background thread read from it.

The other issue was the AppKit version direct called in to NSApplication and made no attempt at being thread safe, so this object had different amounts of safety depending on the platform.

This PR separates these two behaviors, so SentryApplication is just the system API wrapping (with some extra post-processing on system APIs) and ThreadsafeApplication is a UIKit only thread safe API. This ThreadsafeApplication now uses locks to ensure there isn't a data race. Luckily our code was not relying on the macOS version being thread safe, and now that is just more clear at compile time.

#skip-changelog

[codecov]

Codecov Report

❌ Patch coverage is 41.11111% with 106 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.653%. Comparing base (3ffd0e5) to head (c2e34f8).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/Swift/Helper/SentryApplication+UIKit.swift	20.769%	103 Missing ⚠️
Sources/Swift/Helper/ThreadSafeApplication.swift	90.625%	3 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #5900       +/-   ##
=============================================
- Coverage   86.752%   86.653%   -0.099%     
=============================================
  Files          428       429        +1     
  Lines        36882     36857       -25     
  Branches     17412     17396       -16     
=============================================
- Hits         31996     31938       -58     
- Misses        4839      4873       +34     
+ Partials        47        46        -1     

Files with missing lines	Coverage Δ
Sources/Sentry/SentryANRTrackingIntegration.m	98.809% <100.000%> (-0.596%)	⬇️
Sources/Sentry/SentryClient.m	98.944% <100.000%> (ø)
Sources/Sentry/SentryCrashIntegration.m	99.200% <ø> (ø)
Sources/Sentry/SentryCrashWrapper.m	91.200% <100.000%> (+0.070%)	⬆️
Sources/Sentry/SentryDependencyContainer.m	88.584% <100.000%> (+0.052%)	⬆️
...rces/Sentry/SentryDependencyContainerSwiftHelper.m	100.000% <100.000%> (ø)
Sources/Sentry/SentrySDKInternal.m	86.885% <ø> (ø)
Sources/Sentry/SentrySessionReplayIntegration.m	87.108% <100.000%> (+0.047%)	⬆️
Sources/Sentry/SentrySessionTracker.m	99.137% <100.000%> (ø)
Sources/Sentry/SentryTracer.m	97.049% <ø> (-1.148%)	⬇️
... and 4 more

... and 4 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1223.92 ms	1248.04 ms	24.13 ms
Size	23.75 KiB	953.91 KiB	930.16 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
2609f7a	1218.17 ms	1241.34 ms	23.17 ms
ad964ca	1234.73 ms	1254.88 ms	20.15 ms
c6c1cb7	1235.71 ms	1263.80 ms	28.08 ms
5258fb8	1207.92 ms	1234.51 ms	26.59 ms
efab7d3	1219.98 ms	1252.12 ms	32.14 ms
83bb978	1238.33 ms	1260.04 ms	21.71 ms
0ee162c	1226.90 ms	1261.72 ms	34.83 ms
c6d2354	1226.53 ms	1252.69 ms	26.16 ms
2de3f92	1207.56 ms	1234.96 ms	27.40 ms
f8029e2	1245.16 ms	1261.32 ms	16.16 ms

App size

Revision	Plain	With Sentry	Diff
2609f7a	23.75 KiB	867.04 KiB	843.29 KiB
ad964ca	23.75 KiB	913.17 KiB	889.42 KiB
c6c1cb7	23.75 KiB	928.15 KiB	904.40 KiB
5258fb8	23.75 KiB	874.45 KiB	850.70 KiB
efab7d3	23.75 KiB	912.78 KiB	889.03 KiB
83bb978	23.75 KiB	920.64 KiB	896.89 KiB
0ee162c	23.75 KiB	933.33 KiB	909.58 KiB
c6d2354	23.75 KiB	919.70 KiB	895.95 KiB
2de3f92	23.75 KiB	919.69 KiB	895.94 KiB
f8029e2	23.75 KiB	893.72 KiB	869.97 KiB

Previous results on branch: updateApplication

Startup times

Revision	Plain	With Sentry	Diff
e2a0e66	1198.58 ms	1231.93 ms	33.35 ms
8ce26a2	1225.54 ms	1242.65 ms	17.10 ms
ee17551	1217.88 ms	1245.02 ms	27.14 ms
621c433	1219.33 ms	1246.92 ms	27.59 ms
289850d	1216.71 ms	1239.00 ms	22.29 ms

App size

Revision	Plain	With Sentry	Diff
e2a0e66	23.75 KiB	928.30 KiB	904.55 KiB
8ce26a2	23.75 KiB	928.00 KiB	904.25 KiB
ee17551	23.75 KiB	928.53 KiB	904.78 KiB
621c433	23.75 KiB	928.56 KiB	904.81 KiB
289850d	23.75 KiB	928.00 KiB	904.25 KiB

[ohwhen]

🔥

[philprime]

Good progress, let some comments

[philprime]

LGTM

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentryUIViewControllerSwizzling.m