feat: Metrics support

[limbonaut]

Adds support for emitting custom metrics to Sentry — track counters, gauges, and distributions directly from GDScript.

• Closes Metrics Support #497
• Docs PR docs(godot): Add Metrics documentation sentry-docs#16672

Metrics are enabled by default via options.experimental.enable_metrics and accessible through SentrySDK.metrics.

# Count occurrences
SentrySDK.metrics.count("match_started")
SentrySDK.metrics.count("enemies_spawned", wave_size, {"level": "castle"})

# Track point-in-time values
SentrySDK.metrics.gauge("players_online", lobby.get_player_count())
SentrySDK.metrics.gauge("memory_usage", OS.get_static_memory_usage(), "byte")

# Record value distributions
SentrySDK.metrics.distribution("level_load_time", load_time, "millisecond")

Metrics can be intercepted and modified via options.experimental.before_send_metric.

Supported on Windows, Linux, Android, and Web. Not yet supported on Apple platforms.

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

📋 Changelog Preview

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

---

New Features ✨

• (options) Support SENTRY_DSN, SENTRY_RELEASE, and SENTRY_ENVIRONMENT env vars by limbonaut in #548

• Metrics support by limbonaut in #553

• Add shutdown_timeout_ms option by limbonaut in #539

Bug Fixes 🐛

• (export) Guard export plugins with platform feature checks by limbonaut in #557

Documentation 📚

• Add README files for addon and demo project packages by limbonaut in #547
• Update Web platform support information in README by limbonaut in #536

Internal Changes 🔧

Deps

• Update Sentry Android to v8.34.0 by github-actions in #561
• Update Sentry JavaScript to v10.42.0 by github-actions in #560
• Bump serialize-javascript and terser-webpack-plugin in /src/sentry/javascript/bridge by dependabot in #559
• Update Sentry JavaScript to v10.41.0 by github-actions in #555
• Update Native SDK to v0.13.1 by github-actions in #544
• Update Native SDK to v0.13.0 by github-actions in #533
• Update Sentry Android to v8.33.0 by github-actions in #531
• Update wasm-split to v26.2.1 by github-actions in #534
• Update Sentry JavaScript to v10.40.0 by github-actions in #540

Other

• (web) Optimize file attachment loading in WASM bridge by limbonaut in #538
• Add .clangd to .gitignore by limbonaut in #552
• Use better AssetLib icon by limbonaut in #549
• Add GH_TOKEN and harden AssetLib workflow by limbonaut in #546
• Automate AssetLib updates on release by limbonaut in #545
• Generate a separate package with demo project by limbonaut in #542
• Exclude MSVC linker byproducts from build artifact by limbonaut in #543
• Run CI on all PRs regardless of changed paths by limbonaut in #541

---

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

[github-actions]

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

Generated by 🚫 dangerJS against 7b6198c

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

[limbonaut]

I'll extract 865b84c as separate PR, so we don't have to wait on native release.