feat(metrics): [Trace Metrics 15] Android Metrics batch processor and factory

[adinauer]

📜 Description

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[adinauer]

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• feat(metrics): [Trace Metrics 27] Automatically use SentryOptions.Metrics.BeforeSendMetricCallback Spring beans #5021 : 2 dependent PRs (#5022 , #5024 )
• feat(metrics): [Trace Metrics 26] SentryMetricsParameters create shortcut for attributes map #5020
• feat(metrics): [Trace Metrics 25] Add Hint to Metrics #5019
• feat(metrics): [Trace Metrics 24] PR Feedback #5013
• feat(metrics): [Trace Metrics 23] Add E2E tests for Metrics #5011
• feat(metrics): [Trace Metrics 22] Close and flush MetricsBatchProcessor from SentryClient #5010
• Use uv for managing python version #5009
• feat(metrics): [Trace Metrics 21] Add AI rules files for Metrics (and update feature flags rule) #5008
• feat(metrics): [Trace Metrics 20] Add device and OS attributes to metrics #5007
• feat(metrics): [Trace Metrics 19] Create SentryMetricsParameters for Metrics #5006
• feat(metrics): [Trace Metrics 18] Add unit tests for Metrics #5005
• feat(metrics): [Trace Metrics 17] Remove Experimental Annotation from Metrics Options #4996
• feat(metrics): [Trace Metrics 16] Only send user attributes if sendDefaultPii is true #4995
• feat(metrics): [Trace Metrics 15] Android Metrics batch processor and factory #4994 👈 (View in Graphite)
• feat(metrics): [Trace Metrics 14] Metrics Manifest options for Android #4993
• feat(metrics): [Trace Metrics 13] Metrics external options #4992
• feat(metrics): [Trace Metrics 12] Record client report for discarded metrics envelope item #4991
• feat(metrics): [Trace Metrics 11] Metrics Envelope item deserialization #4990
• feat(metrics): [Trace Metrics 10] Metrics Gauge API #4989
• feat(metrics): [Trace Metrics 9] Metrics Distribution API #4988
• feat(metrics): [Trace Metrics 8] Metrics Count API #4987
• feat(metrics): [Trace Metrics 7] Metrics counter basic API #4986
• feat(metrics): [Trace Metrics 6] Implement SentryClient for Metrics #4985
• feat(metrics): [Trace Metrics 5] Add batch processor for Metrics #4984
• feat(metrics): [Trace Metrics 4] Add transport types for metrics #4983
• feat(metrics): [Trace Metrics 3] Enable metrics by default #4982
• feat(metrics): [Trace Metrics 2] MetricsApi stub #4981
• feat(metrics): [Trace Metrics 1] Metrics Options #4980
• main

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[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

### Features

- [Trace Metrics 15] Android Metrics batch processor and factory ([#4994](https://github.com/getsentry/sentry-java/pull/4994))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description or adding a skip-changelog label.

Generated by 🚫 dangerJS against 56879b3

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	320.31 ms	353.78 ms	33.47 ms
Size	1.58 MiB	2.20 MiB	635.46 KiB

[sentry]

Bug: The SentryClient does not call close() or flush() on the new metricsBatchProcessor during shutdown, leading to memory leaks, data loss, and potential runtime errors.
_{Severity: CRITICAL}

Suggested Fix

In SentryClient.java, add a call to metricsBatchProcessor.flush(timeoutMillis) within the flush() method and a call to metricsBatchProcessor.close(isRestarting) within the close() method. This will mirror the existing cleanup logic for loggerBatchProcessor.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location:
sentry-android-core/src/main/java/io/sentry/android/core/AndroidMetricsBatchProcessor.java#L21

Potential issue: When metrics are enabled, the `SentryClient` initializes a
`metricsBatchProcessor` but fails to clean it up during shutdown. The
`SentryClient.close()` method does not call `metricsBatchProcessor.close()`, and
`SentryClient.flush()` does not call `metricsBatchProcessor.flush()`. This leads to
several issues on Android: a memory leak because the `AndroidMetricsBatchProcessor`
remains registered as an `AppStateListener`, potential runtime errors if the app
backgrounds after the client is closed, and data loss as queued metrics are never
flushed.

_{Did we get this right? 👍 / 👎 to inform future reviews.}