poc: android anr

[bitsandfoxes]

wip

capture anr on unity main thread with stack trace

relies on

• poc: hearbeat anr sentry-java#5431
• poc: thread sampling sentry-native#1721

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

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

- android anr ([#2681](https://github.com/getsentry/sentry-unity/pull/2681))

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