refactor: Add null-handling to multiple types

[philprime]

This PR is derived from #5572 in an effort to make the large amount of changes easier to review for #5577.

Another round of nullability-related changes.

#skip-changelog

[codecov]

Codecov Report

❌ Patch coverage is 93.93939% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.684%. Comparing base (e8da57d) to head (aaa619b).
⚠️ Report is 10 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
Sources/Sentry/SentryUserFeedbackIntegration.m	0.000%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #5906       +/-   ##
=============================================
+ Coverage   86.659%   86.684%   +0.025%     
=============================================
  Files          423       423               
  Lines        36527     36567       +40     
  Branches     17280     17317       +37     
=============================================
+ Hits         31654     31698       +44     
+ Misses        4828      4824        -4     
  Partials        45        45               

Files with missing lines	Coverage Δ
Sources/Sentry/SentryBinaryImageCache.m	96.000% <100.000%> (ø)
Sources/Sentry/SentryBreadcrumb.m	97.087% <100.000%> (+0.117%)	⬆️
Sources/Sentry/SentryBreadcrumbTracker.m	87.317% <100.000%> (+0.062%)	⬆️
Sources/Sentry/SentryClient.m	98.521% <100.000%> (+0.001%)	⬆️
Sources/Sentry/SentryCoreDataTracker.m	97.959% <100.000%> (ø)
Sources/Sentry/SentryDebugImageProvider.m	89.051% <100.000%> (+0.679%)	⬆️
Sources/Sentry/SentryDevice.m	34.513% <100.000%> (ø)
Sources/Sentry/SentryProfiler.mm	91.011% <100.000%> (+0.259%)	⬆️
Sources/Sentry/SentryUserFeedbackIntegration.m	25.000% <0.000%> (-1.316%)	⬇️

... and 4 files with indirect coverage changes

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1239.12 ms	1266.85 ms	27.73 ms
Size	23.75 KiB	919.82 KiB	896.07 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
2bddb03	1214.11 ms	1246.78 ms	32.67 ms
aa0b738	1236.78 ms	1253.08 ms	16.31 ms
0b5fd21	1237.52 ms	1251.36 ms	13.84 ms
f97a070	1218.88 ms	1253.12 ms	34.24 ms
605fa27	1226.31 ms	1251.35 ms	25.05 ms
8da82b4	1220.08 ms	1248.24 ms	28.16 ms
ebc72be	1221.24 ms	1249.66 ms	28.42 ms
37183fe	1212.33 ms	1238.92 ms	26.59 ms
80a5166	1224.49 ms	1251.29 ms	26.80 ms
b13e93a	1236.24 ms	1247.33 ms	11.08 ms

App size

Revision	Plain	With Sentry	Diff
2bddb03	23.75 KiB	891.01 KiB	867.26 KiB
aa0b738	23.74 KiB	872.75 KiB	849.00 KiB
0b5fd21	23.75 KiB	912.78 KiB	889.03 KiB
f97a070	23.75 KiB	858.68 KiB	834.93 KiB
605fa27	23.75 KiB	908.03 KiB	884.28 KiB
8da82b4	23.75 KiB	913.63 KiB	889.88 KiB
ebc72be	23.75 KiB	908.22 KiB	884.47 KiB
37183fe	23.75 KiB	913.63 KiB	889.87 KiB
80a5166	23.75 KiB	904.53 KiB	880.78 KiB
b13e93a	23.75 KiB	855.37 KiB	831.62 KiB

Previous results on branch: philprime/strict-nullability-1

Startup times

Revision	Plain	With Sentry	Diff
3df09ef	1229.06 ms	1249.94 ms	20.88 ms
64bc73c	1219.28 ms	1248.39 ms	29.11 ms

App size

Revision	Plain	With Sentry	Diff
3df09ef	23.75 KiB	919.62 KiB	895.87 KiB
64bc73c	23.75 KiB	908.02 KiB	884.27 KiB

[philipphofmann]

LGTM