[Feature] Lazy load `agate`

[dwreeves]

Is this your first time submitting a feature request?

• [X] I have read the expectations for open source contributors
• [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-redshift functionality, rather than a Big Idea better suited to a discussion

Describe the feature

Required to get full functionality out of this. https://github.com/dbt-labs/dbt-adapters/pull/126

Describe alternatives you've considered

No response

Who will this benefit?

No response

Are you interested in contributing this feature?

Yeah

Anything else?

No response