Updates the dynamic block in load balancer modules to make OAuth2 client fields optional.
This allows enabling Google-Managed IAP by omitting these fields or passing .
Supports migration path by passing as per Google documentation.
Added test case to to verify configuration.
* feat: Changes for migrating resources to GLB module
* Updated Readme
* Added support for null description
* Added support for empty string
* Added default optional values
* Changed Readme
* Corrected description according to readme
* Added name and description changes for net-lb-app-ext-regional
* Added name and description changes for net-lb-app-int
* Added name and description changes for net-lb-app-int-cross-region
* Added name and description changes for net-lb-proxy-int
* Added name and description changes for net-lb-ext
* Added name and description changes for net-lb-int
* Changed Readme docs