Add support for timezone in jsonData for MySQL data source

[daha]

Description

Add support for the new field timezone, in jsonData, used by the MySQL data source:
https://grafana.com/docs/grafana/latest/datasources/mysql/

Relevant issues/tickets

None

Type of change

Not sure if this is breaking or not. It whitelists one field in jsonData in the datasource CRD.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• This change requires a documentation update
• I have added tests that prove my fix is effective or that my feature works
• I have added a test case that will be used to verify my changes
• Verified independently on a cluster by reviewer

Verification steps

• Create datasource with the field timestamp in jsonData and verify that the timezone is present in the datasource.

[HVBE]

LGTM!