Add starts with to show objects like for performance boost

[aranke]

Problem

show objects is slow in large schemas where many objects match name (e.g., stg_metrics).

Solution

Add starts with to the end of the query to speed it up.
On ad-hoc testing, I'm seeing a 10x speed-up (2s → 0.2s).

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

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-snowflake contributing guide.

[aranke]

False alarm, looks like the results are dependent on whether Snowflake is throttling metadata queries: https://community.snowflake.com/s/article/metadata-operations-throttling.

I don't think I can improve this macro further, closing this PR.