Isolating distribution testing

[leahwicz]

resolves #1290

Problem

We validate wheel and source distributions in the same environment during the build validation step. This led to issues documented here dbt-labs/dbt-core#10465.

Solution

This is the same solution as what we did in dbt-snowflake first: dbt-labs/dbt-snowflake#1161
This is to bring parity to the other repos as well.

This is a test run of the Action running with the installation and testing of wheels and source distributions split into separate Actions Jobs that isolate them from one another: https://github.com/leahwicz/dbt-bigquery/actions/runs/10821506800/job/30023648113

Checklist

• 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
• 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