[ADAP-385] [Bug] Negative `part_number` for `dbt.split_part()` is not working

[dave-connors-3]

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-spark functionality, rather than a Big Idea better suited to a discussion

Describe the feature

like other adapters, this adapter should support negative arguments for part_number in it's implementation of the split_part cross db util.

See details in https://github.com/dbt-labs/dbt-bigquery/issues/615

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