Allow defining service groups where cross cutting configuration can be applied

[davidfowl]

If I want to apply environment variables to a set of services, it should be possible to configure them in a group where those get applied. e.g.

Today

var builder = DistributedApplication.CreateBuilder();

builder.AddProject<P1>()
       .WithEnvironment("shared", "shared value")
       .WithEnvironment("unique", "1") ;

builder.AddProject<P2>()
       .WithEnvironment("shared", "shared value")
       .WithEnvironment("unique", "2") ;


builder.AddProject<P3>()
       .WithEnvironment("shared", "shared value")
       .WithEnvironment("unique", "3") ;

builder.Build().Run();

After

var builder = DistributedApplication.CreateBuilder();

var group = builder.CreateGroup();

group.WithEnvironment("shared", "shared value");

group.AddProject<P1>()
     .WithEnvironment("unique", "1") ;

group.AddProject<P2>()
     .WithEnvironment("unique", "2") ;

group.AddProject<P3>()
     .WithEnvironment("unique", "3") ;

builder.Build().Run();

[mitchdenny]

Do you want this in GA, I'm assuming this is post GA now?