Fix UncaughtExceptionHandlerIntegration Memory Leak

[lbloder]

Upon registration check if an UncaughtExceptionHandlerIntegration is already set as defaultUncaughtExceptionHandler, if so, set its defaultExceptionHandler as the default of the new UncaughtExceptionHandlerIntegration.

💡 Motivation and Context

Fixes #3266

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code.
• 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.
• 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	439.76 ms	521.98 ms	82.22 ms
Size	1.70 MiB	2.28 MiB	592.31 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
4e260b3	388.40 ms	468.98 ms	80.58 ms
0bd723b	375.20 ms	452.41 ms	77.20 ms
baaf637	462.32 ms	579.22 ms	116.90 ms
8838e01	367.65 ms	447.40 ms	79.75 ms
c7e2fbc	393.98 ms	478.24 ms	84.27 ms
b172d4e	352.92 ms	446.50 ms	93.58 ms
93a76ca	397.30 ms	455.16 ms	57.87 ms
93a76ca	377.41 ms	448.22 ms	70.81 ms
7b7964f	401.31 ms	513.78 ms	112.46 ms
c554ca2	364.98 ms	433.64 ms	68.66 ms

App size

Revision	Plain	With Sentry	Diff
4e260b3	1.72 MiB	2.27 MiB	554.95 KiB
0bd723b	1.72 MiB	2.29 MiB	578.09 KiB
baaf637	1.72 MiB	2.27 MiB	558.42 KiB
8838e01	1.72 MiB	2.29 MiB	578.15 KiB
c7e2fbc	1.72 MiB	2.29 MiB	576.40 KiB
b172d4e	1.72 MiB	2.29 MiB	578.09 KiB
93a76ca	1.72 MiB	2.29 MiB	576.75 KiB
93a76ca	1.72 MiB	2.29 MiB	576.75 KiB
7b7964f	1.70 MiB	2.28 MiB	592.12 KiB
c554ca2	1.70 MiB	2.27 MiB	582.25 KiB

Previous results on branch: fix/uncaughtexceptionhandler-memory-leak

Startup times

Revision	Plain	With Sentry	Diff
24b2a89	397.32 ms	462.63 ms	65.31 ms
e73aac6	426.27 ms	471.55 ms	45.29 ms

App size

Revision	Plain	With Sentry	Diff
24b2a89	1.70 MiB	2.28 MiB	592.31 KiB
e73aac6	1.70 MiB	2.28 MiB	592.31 KiB

[romtsn]

Suggested change

	// defaultExceptionHandler = currentHandler;

[romtsn]

nice!

[adinauer]

Thanks for taking care of this!