chore: move migrations to rust

also adds some basic test seed data

PluralKit.Core/Database/Migrations/43.sql

@@ -1,6 +0,0 @@
--- database version 43
--- add config setting for padding 5-character IDs in lists
-
-alter table system_config add column hid_list_padding int not null default 0;
-
-update info set schema_version = 43;