Need the ability to set HTTP 2.0 Proxy configuration for App Service resources

**Is your feature request related to a problem? Please describe.**
Currently, there are two configurations in a Linux App Service relating to HTTP 2.0 support, one to set the HTTP Version and one to set the HTTP 2.0 proxy type. In Bicep, I can see the appropriate property to set the HTTP version (`http20Enabled`). However, I have not been able to find a matching property for the proxy type.


It looks like this issue has already been noted in a Terraform Github issue where it sounds like the root cause is that the property is missing in the Microsoft.Web API, but I wanted to also raise the issue here as well in case the Bicep team has better success getting the issue on the appropriate team's radar. https://github.com/hashicorp/terraform-provider-azurerm/issues/18883

**Describe the solution you'd like**
A Bicep property on the App Service (Microsoft.Web/sites) resource named something similar to `http20Proxy` with allowed properties on, off, and gRPC only

The issue concerns Microsoft.Web/sites and the existing http20Enabled property; start by checking the Microsoft.Web API and the current App Service type definitions. Done means the proxy configuration is supported with on, off, and gRPC-only values, if the upstream API exposes it.

Written by the indexing model from the issue text.