feat(misconf): add support for Terraform Az Database flexible server resources

[nikpivkin]

Our current implementation parses several legacy Azure Database Terraform resources, all of which have been deprecated and replaced by their Flexible Server equivalents:

• azurerm_postgresql_server → replaced by azurerm_postgresql_flexible_server
• azurerm_postgresql_firewall_rule → replaced by azurerm_postgresql_flexible_server_firewall_rule
• azurerm_postgresql_configuration → replaced by azurerm_postgresql_flexible_server_configuration
• azurerm_mysql_server → replaced by azurerm_mysql_flexible_server

We need to add full support for all corresponding Flexible Server resources while maintaining backward compatibility with the existing parsing logic for legacy resources.

Additionally, for azurerm_mysql_server, we previously extracted server configuration and firewall rules directly from the single resource. The new Flexible Server model introduces standalone resources — azurerm_mysql_flexible_server_firewall_rule and azurerm_mysql_flexible_server_configuration — which must now also be parsed and handled appropriately.