Exclude statuses from index that is not searchable by local user

[tribela]

Currently, searchable_by field contains all related accounts that contains remote user.
But remote user cannot perform a search on local instance.

This PR makes that ES index only contain statuses that searchable by at least one local user.
This slightly increase DB query at insert a status, But decrease ES volume massively(because most of remote status doesn't containing a mention to local user)

[Gargron]

This is an n+1 query which is why the indexing becomes slower. It also loads all account objects into memory before filtering them with Ruby instead of only selecting local accounts with SQL.

Instead, you can change the crutch definitions in chewy/statuses_index.rb to filter for local accounts in the first place.

For example:

data = ::Mention.where(status_id: collection.map(&:id)).where(account: Account.local).pluck(:status_id, :account_id)