.NET: Generate a binary version of runtimeconfig.json for mobile targets

[rolfbjarne]

We need to generate a binary version of runtimeconfig.json for certain features to work.

Steps:

• Use Mono's task to convert *.runtimeconfig.json to a binary blob.
• Bundle the blob in the .app
• Don't bundle the json in the app.

Ref: #11693 (comment)
Ref: https://github.com/dotnet/runtime/blob/01b7e73cd378145264a7cb7a09365b41ed42b240/docs/design/mono/mobile-runtimeconfig-json.md
Ref: dotnet/runtime#49237
Ref: dotnet/android#6009

[rolfbjarne]

@jonathanpeppers I believe this is something XA should be doing too.

[jonathanpeppers]

We just got: dotnet/android#5975

I think we can start using the <RuntimeConfigParser/> task now:

https://github.com/dotnet/runtime/blob/main/src/tasks/RuntimeConfigParser/RuntimeConfigParser.cs

We probably won't get this until Preview 6 or later.