Forbid main thread queries from room

[TimoPtr]

Summary

In theory everything is now interacting with the database in the main thread. We might have forget some usages, but a good way to find them would be to try to remove this option on room that allow the queries to happen on the main thread.

Checklist

• New or updated tests have been added to cover the changes following the testing guidelines.
• The code follows the project's code style and best_practices.
• The changes have been thoroughly tested, and edge cases have been considered.
• Changes are backward compatible whenever feasible. Any breaking changes are documented in the changelog for users and/or in the code for developers depending on the relevance.

Any other notes

[jpelgrom]

Makes me wonder why it was ever set to allow this in the first place, as Rooms default is to not allow this.

[TimoPtr]

Makes me wonder why it was ever set to allow this in the first place, as Rooms default is to not allow this.

It was added in July 2020 #633 I think no one ever noticed the option.