[8.x] Allow parallel testing without database creation

[uintaam]

Adding the ability to bypass database creation in parallel tests completely.

Allows parallel testing to move forward without a custom database setup for each parallel process.

Allows applications to do their own custom database setup without requiring database setup.

• In our case, we run all migrations as part of our Docker setup.
• In cases where there is more than one MySQL DB per connection, this can be useful as the current system doesn't support creating multiple databases on the default connection.