ER: Use Secrets to store source db password for Postgres

### Enhancement Request Details

The DB password for Postgres is being stored as plaintext. This should be stored as a secret.

Changes required:

- Table `configs` should have a `password_secret_id` field instead of the plaintext password
- ConfigEditor for DMS should accept a **Password Secret ID** parameter instead of the plaintext password
- When running the deploy, the password should be retrieved from Secrets API using the `password_secret_id` stored in the config.

### Version

None

### What database engine is this documentation change for?

None

### Relevant log output

_No response_