Diagnostics: surface information regarding namespaces with . in them

[Druue]

Pre-requisite:

Test if dots are indeed allowed in the namespace name across providers

• coackroachdb
• mongodb
• mysql
• postgresql
• sqlite
• sqlserver

Todo:

If dots are allowed:

• improve the rust error message
  • currently a table not found error when a user is trying to refer to their DB
    multiSchema does not work with SQL Server schemas with dot in name (= databases) prisma#15696
• surface a diagnostic tooltip providing context regarding dots in Prisma schema namespaces

Else:
Surface a diagnostic error saying . is invalid in namespace names or something