Update documentation on Advanced Database Configuration in each documentation

**Description:**

Changing to MySQL/ Postgre/ etc these documents have advanced database configuration parameters. But there is no documentation on how to decide on these parameters. The values provided in the documentation may not be the ideal values. 

https://github.com/wso2-enterprise/iam-cloud-product/issues/163


https://is.docs.wso2.com/en/latest/setup/changing-to-mysql/