feat: Add parentSpanIsAlwaysRootSpan is true by default

[krystofwoldrich]

📢 Type of change

• New feature
• Enhancement

📜 Description

Add parentSpanIsAlwaysRootSpan default true to align with JS v8 browser client.

https://github.com/getsentry/sentry-javascript/blob/d265d927ee87d5c50fdebc62da926ddea3c95912/packages/browser/src/client.ts#L57

💚 How did you test it?

unit tests

📝 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
• All tests passing
• No breaking changes

[github-actions]

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

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

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

- Add `parentSpanIsAlwaysRootSpan` is `true` by default ([#4084](https://github.com/getsentry/sentry-react-native/pull/4084))

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 79f4cff

[lucas-zimerman]

LGTM!

[github-actions]

iOS (legacy) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1235.51 ms	1237.57 ms	2.06 ms
Size	2.36 MiB	3.08 MiB	733.34 KiB

Baseline results on branch: v6

Startup times

Revision	Plain	With Sentry	Diff
f77a902+dirty	1227.09 ms	1226.74 ms	-0.35 ms

App size

Revision	Plain	With Sentry	Diff
f77a902+dirty	2.36 MiB	3.08 MiB	733.32 KiB

[github-actions]

Android (new) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	398.29 ms	443.88 ms	45.59 ms
Size	7.15 MiB	8.34 MiB	1.19 MiB

Baseline results on branch: v6

Startup times

Revision	Plain	With Sentry	Diff
f77a902+dirty	478.49 ms	516.40 ms	37.91 ms

App size

Revision	Plain	With Sentry	Diff
f77a902+dirty	7.15 MiB	8.34 MiB	1.19 MiB

[github-actions]

iOS (new) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1234.29 ms	1241.67 ms	7.39 ms
Size	2.92 MiB	3.64 MiB	739.18 KiB

Baseline results on branch: v6

Startup times

Revision	Plain	With Sentry	Diff
f77a902+dirty	1223.83 ms	1227.98 ms	4.15 ms

App size

Revision	Plain	With Sentry	Diff
f77a902+dirty	2.92 MiB	3.64 MiB	739.16 KiB