WIP Update to Kotlin 1.6

[grigoryk]

Still working through the tests (see https://github.com/Kotlin/kotlinx.coroutines/blob/master/kotlinx-coroutines-test/MIGRATION.md)

Pull Request checklist

• Quality: This PR builds and passes detekt/ktlint checks (A pre-push hook is recommended)
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry or does not need one
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features

After merge

• Milestone: Make sure issues closed by this pull request are added to the milestone of the version currently in development.
• Breaking Changes: If this is a breaking change, please push a draft PR on Reference Browser to address the breaking issues.

[jonalmeida]

Was hoping for a final release of the Compose upgrade, but we got an RC03 instead.

[jonalmeida]

Stable release is out! 🎉

[grigoryk]

Fenix side of this work: mozilla-mobile/fenix#23736

[Mugurell]

@grigoryk #11754 Would update to latest compose and kotlin versions.
Seems like the test are still passing without updating to the newest kotlin-coroutines-test being a blocker.
I've created #11755 for updating the tests before knowing of this PR.

[mergify]

This pull request has conflicts when rebasing. Could you fix it @grigoryk? 🙏

[csadilek]

Just adding a note that this is blocked on finding the cause of mozilla-mobile/fenix#23989 which was triggered by the (since reverted) upgrade of compose to 1.1.0.

[mergify]

This pull request has conflicts when rebasing. Could you fix it @grigoryk? 🙏

[Mugurell]

Will work on adding this on top of #12000 and continue with what's left.

[csadilek]

This will be completed in #12006.