[Feature] Support refresh_token in profiles.yml for Snowflake OAuth authentication

### Is this your first time submitting a feature request?

- [x] I have read the [expectations for open source contributors](https://docs.getdbt.com/docs/contributing/oss-expectations)
- [x] I have searched the existing issues, and I could not find an existing issue for this feature
- [x] I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

### Describe the feature

I'm setting up Snowflake OAuth authentication in dbt core and it looks like dbt doesn't currently support the `refresh_token` variable. The `token` variable asks for an access token value to establish OAuth access. Can dbt add the possibility to enter a refresh token and automatically exchange it for an access token?

### Describe alternatives you've considered

_No response_

### Who will this benefit?

_No response_

### Are you interested in contributing this feature?

_No response_

### Anything else?

_No response_

Start by locating dbt core’s Snowflake OAuth profile and token-auth entry points, then trace how profiles.yml values are parsed and used. Done means refresh_token can be configured and exchanged for an access token, with coverage for that configuration path.

Written by the indexing model from the issue text.