fix: Fix removing value from context not updating observer context

[philprime]

📜 Description

Replaces setExtras to setContext of scope observers when removing a value from scope.
Moves existing test from Objective-C to Swift.

💡 Motivation and Context

Fixes #2588

💚 How did you test it?

📝 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.

🔮 Next steps

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.395%. Comparing base (5ce992b) to head (9a05917).

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4960       +/-   ##
=============================================
- Coverage   92.496%   92.395%   -0.101%     
=============================================
  Files          666       666               
  Lines        78924     78971       +47     
  Branches     28576     27725      -851     
=============================================
- Hits         73002     72966       -36     
- Misses        5824      5910       +86     
+ Partials        98        95        -3     

Files with missing lines	Coverage Δ
Sources/Sentry/SentryScope.m	96.889% <100.000%> (ø)
Tests/SentryTests/SentryScopeSwiftTests.swift	99.133% <100.000%> (+0.077%)	⬆️
Tests/SentryTests/SentryScopeTests.m	96.739% <ø> (-0.291%)	⬇️

... and 26 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5ce992b...9a05917. Read the comment docs.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1229.35 ms	1246.73 ms	17.37 ms
Size	22.30 KiB	823.37 KiB	801.06 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
b483671	1217.20 ms	1236.82 ms	19.62 ms
160a2a7	1219.29 ms	1240.96 ms	21.67 ms
005bb4c	1237.38 ms	1255.54 ms	18.16 ms
df50619	1226.11 ms	1244.92 ms	18.81 ms
a2af9fa	1236.29 ms	1251.67 ms	15.38 ms
1ab18c9	1223.94 ms	1237.32 ms	13.38 ms
ae9c51b	1267.73 ms	1272.33 ms	4.59 ms
b9fc537	1211.00 ms	1220.40 ms	9.40 ms
49819af	1263.92 ms	1275.66 ms	11.74 ms
e8f2cfd	1241.90 ms	1258.98 ms	17.08 ms

App size

Revision	Plain	With Sentry	Diff
b483671	20.76 KiB	434.72 KiB	413.96 KiB
160a2a7	21.58 KiB	614.86 KiB	593.28 KiB
005bb4c	20.76 KiB	419.70 KiB	398.94 KiB
df50619	21.58 KiB	671.57 KiB	649.99 KiB
a2af9fa	20.76 KiB	432.88 KiB	412.11 KiB
1ab18c9	21.90 KiB	727.73 KiB	705.83 KiB
ae9c51b	22.85 KiB	411.13 KiB	388.28 KiB
b9fc537	21.58 KiB	676.19 KiB	654.61 KiB
49819af	20.76 KiB	427.31 KiB	406.55 KiB
e8f2cfd	22.31 KiB	756.67 KiB	734.37 KiB