New scheme for room (replace ArbitraryStorage table and datastore)

Currently the app uses datastore and room, while room only has 2 tables (User and ArbitraryStorage).
It's currently not clear when to use datastore(via AppPreferencesImpl) or ArbitraryStorage.

There should be only room used to store any data.
ArbitraryStorage should be replaced as it contains mixed usecases which is not good (user settings and conversation settings).

A new scheme must be created which for the beginning contains tables for:

• app wide settings
• user wide settings
• conversation settings

while always having in mind that in the long term we also want to have full offline support.

Chat

• Develop offline-first data layer for chat
  • #3630
• Devise and implement DB Schema to enable reading from chat offline
  • #3928
• Create Background job to monitor network connections
• Implement Pull-Based Synchronization to update DB on internet connection.

Conversations

• todo

User Settings

• todo

App Settings

• todo

Start by reading the existing AppPreferencesImpl and ArbitraryStorage usage, then review the completed chat work in issues #3630 and #3928. The intended result is a Room-based scheme covering app-wide, user-wide, and conversation settings, with the remaining Conversations, User Settings, and App Settings work completed and the old mixed storage approach replaced.