Feature Request: Allow optional bypass of Managed Connection Pooling

### Question

We have a Cloud SQL Postgres instance with Managed Connection Pooling enabled in transaction pooling mode. Under most circumstances we would like to connect to this instance via MCP. However, under certain circumstances we need to connect via cloud-sql-proxy directly to port 5432 of the instance, bypassing MCP. This does not seem possible currently as the port configuration options only modify how cloud-sql-proxy listens for client connections.

### Code

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### Additional Details

_No response_