Fixes #9580

* Add moderation warnings

Replace individual routes for disabling, silencing, and suspending
a user, as well as the report update route, with a unified account
action controller that allows you to select an action (none,
disable, silence, suspend) as well as whether it should generate an
e-mail notification with optional custom text. That notification,
with the optional custom text, is saved as a warning.

Additionally, there are warning presets you can configure to save
time when performing the above.

* Use Account#local_username_and_domain

* Add spec for RelayPolicy

* Add specs for SubscriptionPolicy

* Add specs for SettingsPolicy

* Add specs for TagPolicy

* Add specs for ReportPolicy

* Add failing test for windows-1251 link cards

* Ignore low-confidence CharlockHolmes guesses

Fixes #9466

* Fix no method error when charlock holmes cannot detect charset

* Error message for avatar image that's too large. #9204

* Code climate/formatting

* Removed avatar error message

* Moved valid image dimentions check to update service

* removed unnescessary begin block

* code climate formatting

* code climate indent fix

* Make custom emoji domains case sensitive #9351

* Fixup style in downcase_domain to comply with codeclimate.

* switch if! to unless

* Don't use transactions, operate in batches.

Also revert spurious schema change.

* Add specs for ActivityPub::CollectionsController#show

* Raise ActiveRecord::RecordNotFound

Raising ActiveRecord::NotFound raises NameError: uninitialized constant
ActiveRecord::NotFound.

Since dots are not allowed in username,
this spec is no longer needed.