Caching toots (#809)
* Initial timeline cache implementation
* Fix build/DI errors for caching
* Rename timeline entities tables. Add migration. Add DB scheme file.
* Fix uniqueness problem, change offline strategy, improve mapping
* Try to merge in new statuses, fix bottom loading, fix saving spans.
* Fix reblogs IDs, fix inserting elements from top
* Send one more request to get latest timeline statuses
* Give Timeline placeholders string id. Rewrite Either in Kotlin
* Initial placeholder implementation for caching
* Fix crash on removing overlap statuses
* Migrate counters to long
* Remove unused counters. Add minimal TimelineDAOTest
* Fix bug with placeholder ID
* Update cache in response to events. Refactor TimelineCases
* Fix crash, reduce number of placeholders
* Fix crash, fix filtering, improve placeholder handling
* Fix migration, add 8-9 migration test
* Fix initial timeline update, remove more placeholders
* Add cleanup for old statuses
* Fix cleanup
* Delete ExampleInstrumentedTest
* Improve timeline UX regarding caching
* Fix typos
* Fix initial timeline update
* Cleanup/fix initial timeline update
* Workaround for weird behavior of first post on initial tl update.
* Change counter types back to int
* Clear timeline cache on logout
* Fix loading when timeline is completely empty
* Fix androidx migration issues
* Fix tests
* Apply caching feedback
* Save account emojis to cache
* Fix warnings and bugs