RJS-2760: Adding `Realm.shutdown()` and fixing clean exit tests

[kraenhansen]

What, How & Why?

This closes #6555, #5781, #4535, #6096, #6357, #4530, #3616 by adding a static Realm.shutdown method, which closes all Realms, cancels all pending Realm.open calls, clears internal caches, resets the logger and collects garbage.

☑️ ToDos

• [x] 📝 Changelog entry
• [x] 📝 Compatibility label is updated or copied from previous entry
• [x] 📝 Update COMPATIBILITY.md
• [x] 🚦 Tests
• [x] 📦 Updated internal package version in consuming package.jsons (if updating internal packages)
• [x] 📱 Check the React Native/other sample apps work if necessary
• [x] 💥 Breaking label has been applied or is not necessary

[kraenhansen]

Rebased on main which has the changes we need with #6598.

[kraenhansen]

Coverage test is still crashing (#6589) but that's not new - I'll go ahead and merge with it.