refactor(outbox): enforce always one outbox folder per account and remove outboxFolderId from preferences

[rafaeltonholo]

Fixes #8049.

This PR is meant to fix the issue where the Outbox gets removed from the database and inbox gets selected as also an outbox, causing the "IllegalStateException: No outbox_state entry for message with id " notification.

This solution focus on:

• Remove the outboxFolderId reference from the preference store;
• Query the folder's table for the outbox id whenever required, caching it to avoid hitting the database too often;
• Ensure there will be one Outbox folder whenever we request the Outbox id. If there isn't a outbox, the app creates a new one on the fly;
• Remove the reference from the outboxFolderId from the LegacyAccount and LegacyAccountDto.

[rafaeltonholo]

I might squash some commits, the ones with message starting with "use OutboxFolderManager...", to keep it easier to revert in case of need.

[wmontwe]

Thank you for digging into this.

I just some little comments.

[wmontwe]

LGTM