poc: capture screenshots with error envelope

[bitsandfoxes]

This is a refactor to see what it would look like to capture a screenshot at the time of the error instead of sending it at "End Of Frame".

This would also be more technically correct, since with the current implementation the screenshot shows the state of the game AFTER the error happened.
Instead of waiting for EndOfFrame we would keep a screenshot around based on a configurable cadence, and attach that to the error at the time of the error.
This would do a couple of things:

• Every error has a screenshot, not just the first in a given frame
• It does not need to be the exact frame before the error, since the screenshot is not guaranteed to be 100% technical accurate (wasn't right now either, since it got captured AFTER the error).
• We could keep a bunch of them around and construct the session replay from them?

[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

- capture screenshots with error envelope ([#2835](https://github.com/getsentry/sentry-unity/pull/2835))

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 3d2ce29