Review and fix all the existing Terraform rules, error message, policy title and description, remediation descriptions.

[rezoan]

• verified registrieslist.rego
• verified registrieswebhooks.rego
• verified securitycontacts.rego
• verified sql_servers.rego
• removed sql_managedinstance.rego file to avoid confusion as there is no resource available for Azure MI in terraform yet. (Managed SQL database instance hashicorp/terraform-provider-azurerm#1747)
• verified storageaccounts.rego
• verified and added rules for storageblobcontainers.rego
• verified vnetsubnets.rego
• fixed re_match(concat("", ["^.*\\.", resource.name, "\\..*$"]), r.properties.subnet_id); is incorrect and need to match with resource.id as per document which is impossible or need to find some other way for validation #189