test: convert some test code from crashable to failable

[armcknight]

Helps fix #3576

I hit one of these today so just went through and removed some easy ones. There are still almost 603 uses of the force unwrap operator and 154 unchecked array indexes in the test code after these changes.

#skip-changelog

[codecov]

Codecov Report

Attention: Patch coverage is 98.54227% with 5 lines in your changes missing coverage. Please review.

Project coverage is 91.347%. Comparing base (df50619) to head (f3b7098).
Report is 3 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4125       +/-   ##
=============================================
+ Coverage   91.338%   91.347%   +0.008%     
=============================================
  Files          610       608        -2     
  Lines        48421     48308      -113     
  Branches     17351     17356        +5     
=============================================
- Hits         44227     44128       -99     
+ Misses        4101      4088       -13     
+ Partials        93        92        -1     

Files	Coverage Δ
...ts/SentryTests/Helper/SentryFileManagerTests.swift	99.125% <100.000%> (+0.006%)	⬆️
...rformance/CoreData/SentryCoreDataTrackerTest.swift	88.636% <100.000%> (ø)
...reData/SentryCoreDataTrackingIntegrationTest.swift	100.000% <100.000%> (ø)
...ns/Performance/SentryPerformanceTrackerTests.swift	100.000% <100.000%> (ø)
...ions/SentryCrash/SentryCrashIntegrationTests.swift	84.888% <100.000%> (ø)
...SentryWatchdogTerminationsScopeObserverTests.swift	100.000% <100.000%> (ø)
...Tests/Networking/SentryTransportFactoryTests.swift	100.000% <100.000%> (ø)
Tests/SentryTests/PrivateSentrySDKOnlyTests.swift	99.624% <100.000%> (+0.007%)	⬆️
...SentryTests/Protocol/SentryClientReportTests.swift	100.000% <100.000%> (ø)
Tests/SentryTests/Protocol/SentryEventTests.swift	100.000% <100.000%> (ø)
... and 18 more

... and 43 files with indirect coverage changes

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[brustolin]

Thanks. We should keep using this approach, it makes safer tests.