Switch issue.description to code_analyzer

What does this MR do and why?

This MR switches issue.description field's analyzer from standard to code_analyzer. We believe that it's going to improve search quality. This MR also includes examples to test the analyzer.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #421012 (closed)