Authenticate via SSH key instead of password

**Is your feature request related to a problem? Please describe.**
I'd like to authenticate to ClickHouse via SSH key instead of password. I already have multiple users that have been created without password (`... IDENTIFIED BY ssh_key ...`) that needs to run DBT (I'd like to avoid creating a DBT user with password and share credentials around).

**Describe the solution you'd like**
I was thinking the `private_key_file` field can be added to `profiles.yml`, I've seen this solution for Snowflake for example.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
I could help with this if you can point me to the right direction.

Start by tracing how profiles.yml fields are parsed and how the ClickHouse connection is configured. Determine where a private_key_file option would be handled, then verify that users can authenticate with an SSH key without supplying a password and add coverage for the new configuration.

Written by the indexing model from the issue text.