Fix serialization issue with CommandExecution

[benc-db]

Description

dbt Labs detected an issue in their testing where failure was caused by this class that is clearly hashable not having a hash function :/

Checklist

• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [ ] I have updated the CHANGELOG.md and added information about my change to the "dbt-databricks next" section.