Too many refactors in one:

- Allowed adding ephemeral(ish) views and functions
- Moved message_count to a concrete database field
- Moved most proxy logic to a stored procedure
- Moved database files around and refactored schema manager

PluralKit.Core/Migrations/3.sql

@@ -1,15 +0,0 @@
--- Same sort of psuedo-enum due to Dapper limitations. See 2.sql.
--- 1 = autoproxy off
--- 2 = front mode (first fronter)
--- 3 = latch mode (last proxyer)
--- 4 = member mode (specific member)
-alter table system_guild add column autoproxy_mode int check (autoproxy_mode in (1, 2, 3, 4)) not null default 1;
-
--- for member mode
-alter table system_guild add column autoproxy_member int references members (id) on delete set null;
-
--- for latch mode
--- not *really* nullable, null just means old (pre-schema-change) data.
-alter table messages add column guild bigint default null;
-
-update info set schema_version = 3;