[performance] filter model and database table improvements (#4277)

- removes unnecessary fields / columns (created_at, updated_at)
- replaces filter.context_* columns with singular filter.contexts bit field which should save both struct memory and database space
- replaces filter.action string with integer enum type which should save both struct memory and database space
- adds links from filter to filter_* tables with Filter{}.KeywordIDs and Filter{}.StatusIDs fields (this also means we now have those ID slices cached, which reduces some lookups)
- removes account_id fields from filter_* tables, since there's a more direct connection between filter and filter_* tables, and filter.account_id already exists
- refactors a bunch of the filter processor logic to save on code repetition, factor in the above changes, fix a few bugs with missed error returns and bring it more in-line with some of our newer code

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4277
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

internal/gtsmodel/common.go

@@ -17,8 +17,17 @@
 
 package gtsmodel
 
+// smallint is the largest size supported
+// by a PostgreSQL SMALLINT, since an SQLite
+// SMALLINT is actually variable in size.
+type smallint int16
+
 // enumType is the type we (at least, should) use
-// for database enum types. it is the largest size
-// supported by a PostgreSQL SMALLINT, since an
-// SQLite SMALLINT is actually variable in size.
-type enumType int16
+// for database enum types, as smallest int size.
+type enumType smallint
+
+// bitFieldType is the type we use
+// for database int bit fields, at
+// least where the smallest int size
+// will suffice for number of fields.
+type bitFieldType smallint