[V2] [FIX] Update resourceTracingSamplingRate on deferred DatadogProvider initialization

[sbarrio]

What does this PR do?

When using delayedinitialization via the DatadogProvider (giving a basic initialization to the provider and later calling DatadogProvider.Initialize with the full config), if the user was to set resourceTracingSamplingRate via DatadogProvider.initialize(...) this value would end up being ignored by the JS XHRProxy. This was pretty apparent on Android, as the tracing would be stuck at the default 20%. on iOS however this resourceTracingSampligRate would be actually used (nativeInitialization is still called in this path), so the bug was masked.

Motivation

Setting the resourceTracingSamplingRate when using deferred initialization should work.

Additional Notes

Before fix (setting resourceTracingSampligRate on`DatadogProvider.initialize(...)

(Note the sampligPriority being 0)

After fix

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[Copilot]

Pull request overview

Fixes deferred initialization (via DatadogProvider + later DatadogProvider.initialize) so that resourceTracingSamplingRate/first-party-host tracing settings are applied to the already-installed JS XHR instrumentation, preventing Android from being stuck at the default sampling rate.

Changes:

• Added a tracking-context update mechanism (onTrackingUpdate) to the request proxy abstraction and implemented it in XHRProxy by reading sampling/hosts from a mutable context at open() time.
• Introduced DdRumResourceTracking.updateTrackingContext() and invoked it during deferred initialization to re-apply resolved tracing values.
• Extended partial initialization config to accept resourceTracingSamplingRate and added regression tests for XHR sampling rate updates.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/core/src/rum/instrumentation/resourceTracking/requestProxy/XHRProxy/XHRProxy.ts	Makes XHR tracing attributes read from a mutable context and adds onTrackingUpdate.
packages/core/src/rum/instrumentation/resourceTracking/requestProxy/XHRProxy/tests/XHRProxy.test.ts	Adds regression tests validating that updated sampling rate affects subsequent XHRs.
packages/core/src/rum/instrumentation/resourceTracking/requestProxy/interfaces/RequestProxy.ts	Extends the request proxy contract with onTrackingUpdate.
packages/core/src/rum/instrumentation/resourceTracking/DdRumResourceTracking.tsx	Adds updateTrackingContext wrapper to update an installed proxy.
packages/core/src/DdSdkReactNativeConfiguration.tsx	Allows resourceTracingSamplingRate in PartialInitializationConfiguration.
packages/core/src/DdSdkReactNative.tsx	Calls updateTrackingContext during deferred initialization before native init.

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[marco-saia-datadog]

Nice 💯