Setup terraform for Snowflake CI instance

[mikealfare]

Problem

Our existing CI database was setup over the course of several manually run SQL statements. This has made it more difficult to figure out what configurations are needed to run dbt-snowflake. It also requires elevated access even to see what was done in the database. We are currently migrating to a different Snowflake account. This would have been simple if we had scripted our environment.

Solution

Let's take this opportunity to script out the infra required to support dbt-snowflake as well as testing dbt-snowflake in CI. We'll use terraform as both an industry and company standard.

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [ ] I have run this code in development and it appears to resolve the stated issue
• [ ] This PR includes tests, or tests are not required/relevant for this PR
• [x] This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX