Fixes https://github.com/payloadcms/payload/issues/8413 and
https://github.com/payloadcms/payload/issues/6460
- Builds indexes for relationships by default in the SQL schema
- Fixes `unique: true` handling with Postgres / SQLite for every type of
relationships (non-polymorphic. hasMany, polymorphic, polymorphic
hasMany) _note_: disables unique for nested to arrays / blocks
relationships in the `_rels` table.
- adds tests
2.0 PR tha ports only indexes creation
https://github.com/payloadcms/payload/pull/8446, because `unique: true`
could be a breaking change if someone has incosistent unique data in the
database.
1ffb6c3e13