docs: Update docs with new Tracing and Scope APIs (#5508)

[harryautomazione]

What

• Created a new guide docs/tracing.rst for manual instrumentation.
• Added tracing to the main index docs/index.rst.
• Updated docs/api.rst to include missing isolation_scope, get_current_scope, and get_isolation_scope autofunction directives.

Why

Fixes #5508. The documentation needed updates to include the new Scope management and Tracing top-level APIs introduced in Sentry SDK 2.0.

How

• Added conceptual explanations for transactions, spans, and isolation/new scopes.
• Linked existing SDK methods docstrings via Sphinx autodoc.

Testing

• Written and structured using standard Sphinx ReStructuredText format.
• No automated validation run.

Checklist

• Linked the relevant issue (Fixes Update docs #5508).
• Described problem, solution and impact.
• Added or updated tests where appropriate.
• Verified no secrets or sensitive data are introduced.

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

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New Features ✨

• (logging) Separate ignore lists for events/breadcrumbs and sentry logs by sl0thentr0py in #5698

Bug Fixes 🐛

Anthropic

• Set exception info on streaming span when applicable by alexander-alderman-webb in #5683
• Patch AsyncStream.close() and AsyncMessageStream.close() to finish spans by alexander-alderman-webb in #5675
• Patch Stream.close() and MessageStream.close() to finish spans by alexander-alderman-webb in #5674

Documentation 📚

• Update docs with new Tracing and Scope APIs (Update docs #5508) by harryautomazione in #5712

• Add note on AI PRs to CONTRIBUTING.md by sentrivana in #5696

Internal Changes 🔧

• Add -latest alias for each integration test suite by sentrivana in #5706
• Use date-based branch names for toxgen PRs by sentrivana in #5704
• 🤖 Update test matrix with new releases (03/19) by github-actions in #5703
• Add client report tests for span streaming by sentrivana in #5677

Other

• Update CHANGELOG.md by sentrivana in #5685

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_{🤖 This preview updates automatically when you update the PR.}

[harryautomazione]

My apologies to the team for the messy Pull Request. It accidentally bundled commits from multiple unrelated tasks due to a local synchronization issue on my end.

I appreciate @sentrivana closing this to keep the repository clean. I have opened a dedicated and clean PR (#5713) for the specific fix I am working on. Sorry for the noise!