--dbt add snowflake key pair authentication support

[mimoyer21]

Is your feature request related to a problem? Please describe.
I am not able to use the --dbt functionality with snowflake key pair authentication

Describe the solution you'd like
Support the connection method described here: https://docs.getdbt.com/reference/warehouse-setups/snowflake-setup#key-pair-authentication

Describe alternatives you've considered
The only current option is to use password authentication

Additional context
@dlawin asked me to create this issue in this Slack thread

[smitsrr]

Looking also for SSH key authentication method for snowflake.

[leoebfolsom]

A similar question has been asked about Redshift. Should we aggregate all requests for other authentication types in this issue, or do we need separate issues for each warehouse? @dlawin @williebsweet 🙏

[williebsweet]

A similar question has been asked about Redshift. Should we aggregate all requests for other authentication types in this issue, or do we need separate issues for each warehouse? @dlawin @williebsweet 🙏

Open a new one for each db.