fix: Remove internal unknown dict for Breadcrumbs

[philipphofmann]

📜 Description

Remove unknown dict when initializing the crumbs with a dict added in #2820. The Java SDK, for example, implements this pattern to keep unknown JSON properties when deserializing and serializing classes. This allows more flexibility when a hybrid SDK or the native SDK serializes an event to disk, and the Java SDK deserializes this event. With the unknown dict, the Java SDK doesn't need to implement all the properties other SDKs have. We only have this for crumbs on the Cocoa SDK, and it doesn't make sense only to keep it for one class. Instead, we removed it to simplify the code because we would need to implement some complex deserialization logic with Swift Decodable for deserializing events. We can always reconsider this approach, but then we would need to add the unknown property concept for all serializable/decodable classes.

💡 Motivation and Context

Came up in #4785

Communicated to .NET, RN and Flutter on Slack.

💚 How did you test it?

Unit tests.

📝 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

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1216.77 ms	1235.31 ms	18.54 ms
Size	22.31 KiB	780.75 KiB	758.44 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
8f397a7	1219.12 ms	1236.67 ms	17.55 ms
00cbe5c	1233.57 ms	1248.24 ms	14.67 ms
97de6c8	1226.78 ms	1240.98 ms	14.20 ms
72c8d84	1257.34 ms	1276.96 ms	19.62 ms
ef5821b	1253.18 ms	1265.46 ms	12.28 ms
e324230	1230.35 ms	1236.45 ms	6.10 ms
89b12eb	1236.02 ms	1246.63 ms	10.61 ms
7cd187e	1239.02 ms	1261.42 ms	22.40 ms
7f14650	1236.00 ms	1255.66 ms	19.66 ms
1734d1b	1198.69 ms	1221.62 ms	22.93 ms

App size

Revision	Plain	With Sentry	Diff
8f397a7	20.76 KiB	420.55 KiB	399.79 KiB
00cbe5c	21.58 KiB	573.16 KiB	551.58 KiB
97de6c8	21.58 KiB	613.99 KiB	592.41 KiB
72c8d84	22.85 KiB	408.88 KiB	386.03 KiB
ef5821b	21.58 KiB	414.96 KiB	393.37 KiB
e324230	22.85 KiB	408.87 KiB	386.02 KiB
89b12eb	20.76 KiB	432.88 KiB	412.11 KiB
7cd187e	20.76 KiB	401.65 KiB	380.89 KiB
7f14650	22.84 KiB	402.63 KiB	379.78 KiB
1734d1b	21.58 KiB	418.82 KiB	397.24 KiB

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.392%. Comparing base (65547cc) to head (2ba8868).
Report is 3 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4803       +/-   ##
=============================================
- Coverage   91.401%   91.392%   -0.010%     
=============================================
  Files          627       627               
  Lines        74575     74553       -22     
  Branches     26834     26823       -11     
=============================================
- Hits         68163     68136       -27     
- Misses        6316      6321        +5     
  Partials        96        96               

Files with missing lines	Coverage Δ
Sources/Sentry/SentryBreadcrumb.m	96.842% <ø> (+0.445%)	⬆️
...s/SentryTests/Protocol/SentryBreadcrumbTests.swift	100.000% <100.000%> (ø)

... and 7 files with indirect coverage changes

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[philprime]

LGTM

[krystofwoldrich]

RN doesn't use any unknown fields.