refactor: Change type of Swift String constants to NSString

[philprime]

📜 Description

Change the type of constants to NSString.

💡 Motivation and Context

We purposely defined constants such as SentryTraceOrigin, SentrySpanOperation and SentrySpanDataKey in Swift for our long-term effort in migrating to Swift.

Stack traces in #4887 indicate that the bridging of Swift String to NSString might be causing memory issues when used from Objective-C blocks (i.e. useSpan).

This PR is an attempt to reduce the amount of bridging performed.

💚 How did you test it?

Can not be reproduced/tested reliably.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.371%. Comparing base (5ea7b5a) to head (fe714f1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4894       +/-   ##
=============================================
+ Coverage   92.369%   92.371%   +0.001%     
=============================================
  Files          659       659               
  Lines        77548     77549        +1     
  Branches     28079     28081        +2     
=============================================
+ Hits         71631     71633        +2     
+ Misses        5821      5817        -4     
- Partials        96        99        +3     

Files with missing lines	Coverage Δ
...SentryProfilerTests/SentryProfileTestFixture.swift	99.705% <100.000%> (ø)
...rformance/CoreData/SentryCoreDataTrackerTest.swift	88.130% <100.000%> (ø)
...ions/Performance/IO/SentryFileIOTrackerTests.swift	98.546% <100.000%> (ø)
...Network/SentryNetworkTrackerIntegrationTests.swift	70.036% <100.000%> (ø)
...iewController/SentryTimeToDisplayTrackerTest.swift	100.000% <100.000%> (ø)
...ntryTests/Transaction/SentrySpanContextTests.swift	100.000% <100.000%> (ø)
...ts/Transaction/SentryTransactionContextTests.swift	100.000% <100.000%> (ø)

... and 14 files with indirect coverage changes

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[philipphofmann]

The tests are failing. We should investigate how we can avoid this issue from happening again. It doesn't have to be in this PR, but we must come up with something cause it can happen again.

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1209.96 ms	1236.96 ms	27.00 ms
Size	22.31 KiB	821.41 KiB	799.10 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
075a044	1237.26 ms	1255.36 ms	18.10 ms
7fb7afb	1235.00 ms	1256.81 ms	21.81 ms
2b19b82	1212.94 ms	1252.84 ms	39.90 ms
257c2a9	1231.45 ms	1252.12 ms	20.67 ms
6129be5	1215.65 ms	1247.18 ms	31.54 ms
3bf3c92	1236.94 ms	1253.00 ms	16.06 ms
5d6ce0e	1237.10 ms	1257.46 ms	20.36 ms
319f0f5	1229.68 ms	1247.67 ms	17.99 ms
7cd187e	1239.39 ms	1258.02 ms	18.63 ms
48e8c2e	1231.00 ms	1244.52 ms	13.52 ms

App size

Revision	Plain	With Sentry	Diff
075a044	20.76 KiB	420.41 KiB	399.65 KiB
7fb7afb	20.76 KiB	419.69 KiB	398.94 KiB
2b19b82	21.58 KiB	542.18 KiB	520.59 KiB
257c2a9	20.76 KiB	401.36 KiB	380.60 KiB
6129be5	21.58 KiB	418.00 KiB	396.42 KiB
3bf3c92	21.58 KiB	706.06 KiB	684.48 KiB
5d6ce0e	22.85 KiB	405.38 KiB	382.53 KiB
319f0f5	22.30 KiB	749.70 KiB	727.40 KiB
7cd187e	20.76 KiB	401.65 KiB	380.89 KiB
48e8c2e	21.58 KiB	418.44 KiB	396.86 KiB

[philipphofmann]

LGTM, if the tests are green. As already pointed out we should follow up with a strategy to prevent regressions.

[philprime]

As already pointed out we should follow up with a strategy to prevent regressions.

#4897

[philprime]

It keeps failing with flaky UI tests unrelated to the changes. Merging this now.