Add support for MySQL in sqlmetrics

[prathamesh-sonpatki]

• Follow the existing Postgres support in https://github.com/last9/last9-cdk/tree/master/go/sqlmetrics.
• Add required tests for MySQL driver.
• Provide a proof of integration with a Golang binary connecting to MySQL database using the CDK is able to emit database metrics. You can use Docker for this purpose and submit a repo URL where the usage is demonstrated.