Add mockgcp coverage for sqlInstance settings.edition

[yuwenma]

Checklist

• I did not find a related open enhancement request.
• I understand that enhancement requests filed in the GitHub repository are by default low priority.
• If this request is time-sensitive, I have submitted a corresponding issue with GCP support.

Describe the feature or resource

We are moving to the direction of using MockGCP to improve the KCC resource test coverage. Related to #1802

Additional information

MockGCP Guide
Mock sql instance

Importance

No response

[jingyih]

The special behavior of settings.edition field is basically a bug. I don't feel it is worth the time to mimic that behavior in mock. Given that we already added #1823 to cover its behavior against real GCP API, I am going to close this one.