[CHORE] Add trace tab to Example app running React Navigation

[sbarrio]

What does this PR do?

The trace Tab is currently only visible when running the old-arch Example app using React Native Navigation. This PR makes it available as well when using React Navigation.

It also fixes an internal log message that was attempting to print the newly generated spanId, but since at the moment of printing that value is still an unresolved promise the actual log message only displayed [object Object], which does not help much.

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

This PR makes the Trace tab available in the Example app when using React Navigation, and adjusts tracing debug logging so it no longer prints an unresolved Promise as [object Object].

Changes:

• Add a Trace tab to the React Navigation bottom tab navigator in the Example app.
• Update the Example TraceScreen to log the created span id.
• Update DdTrace.startSpan internal debug logging to avoid interpolating an unresolved promise.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/core/src/trace/DdTrace.ts	Adjusts start-span debug log to avoid printing an unresolved promise.
example/src/screens/TraceScreen.tsx	Updates Trace screen imports and adds a debug log of the created span id.
example/src/App.tsx	Adds the Trace screen to the bottom tab navigator.

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