[draft] fix(web): don't create runZoneGuarded on web if it already exists

[buenaflor]

📜 Description

If the sentry init is already set up in a zone, don't create another one internally

We can still keep the onError callback and propagate the user's onError on top of it so we can keep the original behaviour

💡 Motivation and Context

Fixes #1943

💚 How did you test it?

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• No new PII added or SDK only sends newly added PII if sendDefaultPii is enabled
• I updated the docs if needed
• All tests passing
• No breaking changes

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- don't create runZoneGuarded on web if it already exists ([#2088](https://github.com/getsentry/sentry-dart/pull/2088))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against f6fa1ac

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.45%. Comparing base (99b37a6) to head (f6fa1ac).

Files	Patch %	Lines
flutter/lib/src/sentry_flutter.dart	57.14%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2088      +/-   ##
==========================================
+ Coverage   88.64%   92.45%   +3.81%     
==========================================
  Files         223       61     -162     
  Lines        7583     1922    -5661     
==========================================
- Hits         6722     1777    -4945     
+ Misses        861      145     -716     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

Android Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	399.60 ms	545.88 ms	146.27 ms
Size	6.35 MiB	7.34 MiB	1008.55 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
0f067d3	359.56 ms	431.28 ms	71.72 ms
4b943a1	348.17 ms	437.15 ms	88.98 ms
5aba417	355.78 ms	450.39 ms	94.61 ms
b0811cc	580.00 ms	675.69 ms	95.69 ms
04db237	330.16 ms	428.38 ms	98.22 ms
c732386	316.84 ms	390.62 ms	73.78 ms
74e1fdd	398.61 ms	418.43 ms	19.82 ms
453e1bc	320.41 ms	372.73 ms	52.32 ms
051e97a	359.56 ms	426.68 ms	67.12 ms
6fedcab	388.26 ms	487.42 ms	99.16 ms

App size

Revision	Plain	With Sentry	Diff
0f067d3	6.33 MiB	7.30 MiB	992.08 KiB
4b943a1	6.34 MiB	7.28 MiB	968.41 KiB
5aba417	5.94 MiB	6.96 MiB	1.02 MiB
b0811cc	6.33 MiB	7.27 MiB	954.02 KiB
04db237	5.94 MiB	6.95 MiB	1.01 MiB
c732386	6.26 MiB	7.20 MiB	958.78 KiB
74e1fdd	6.33 MiB	7.27 MiB	954.12 KiB
453e1bc	5.94 MiB	6.95 MiB	1.01 MiB
051e97a	6.27 MiB	7.20 MiB	959.09 KiB
6fedcab	6.33 MiB	7.30 MiB	987.83 KiB

Previous results on branch: fix/runzoneguarded

Startup times

Revision	Plain	With Sentry	Diff
34ea139	393.15 ms	462.71 ms	69.57 ms

App size

Revision	Plain	With Sentry	Diff
34ea139	6.35 MiB	7.33 MiB	1005.84 KiB

[github-actions]

iOS Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1227.00 ms	1249.88 ms	22.88 ms
Size	8.33 MiB	9.60 MiB	1.27 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
04bd9e6	1230.78 ms	1250.71 ms	19.94 ms
25161f4	1252.35 ms	1263.84 ms	11.49 ms
4656f10	1247.04 ms	1276.16 ms	29.12 ms
abcdba3	1257.31 ms	1283.49 ms	26.18 ms
2966d88	1251.76 ms	1270.21 ms	18.46 ms
333903e	1251.15 ms	1270.21 ms	19.06 ms
2a0edba	1229.27 ms	1259.54 ms	30.27 ms
89ea268	1252.33 ms	1253.58 ms	1.26 ms
50bdfad	1253.14 ms	1274.54 ms	21.40 ms
5aba417	1265.31 ms	1287.90 ms	22.59 ms

App size

Revision	Plain	With Sentry	Diff
04bd9e6	8.33 MiB	9.61 MiB	1.27 MiB
25161f4	8.28 MiB	9.34 MiB	1.06 MiB
4656f10	8.32 MiB	9.50 MiB	1.19 MiB
abcdba3	8.15 MiB	9.12 MiB	989.76 KiB
2966d88	8.32 MiB	9.38 MiB	1.06 MiB
333903e	8.10 MiB	9.16 MiB	1.06 MiB
2a0edba	8.32 MiB	9.52 MiB	1.20 MiB
89ea268	8.09 MiB	9.16 MiB	1.06 MiB
50bdfad	8.32 MiB	9.43 MiB	1.10 MiB
5aba417	8.16 MiB	9.17 MiB	1.01 MiB

Previous results on branch: fix/runzoneguarded

Startup times

Revision	Plain	With Sentry	Diff
34ea139	1245.20 ms	1262.00 ms	16.80 ms

App size

Revision	Plain	With Sentry	Diff
34ea139	8.33 MiB	9.54 MiB	1.22 MiB