Enable granting Microsoft tenants & GitHub orgs access to dev tunnels

Enable support for granting Microsoft tenants and GitHub organizations access to dev tunnels via an api, e.g.

```csharp
var builder = DistributedApplication.CreateBuilder();

var api = builder.AddProject("api");

var msTunnel = builder.AddDevTunnel("ms-tunnel")
.WithMicrosoftTenantAccess() // Grants access to users in the current MS tenant
.WithReference(api);

var ghTunnel = builder.AddDevTunnel("gh-tunnel")
.WithGitHubOrganizationAccess("dotnet") // Grants access to users in the "dotnet" GitHub organization
.WithReference(api);

builder.Build().Run();
```

I'm not sure it's actually possible to support multiple tunnels running simultaneously with different auth providers, as it seems you can only login to a single provider at a time right now, so the sample above might not actually be possible. If that turns out to be a true limit, then we'd need to figure out how we enforce it in the app model and UX.

Start by tracing the existing AddDevTunnel API and its authentication configuration. Investigate whether multiple tunnels can use different providers simultaneously, then determine how tenant and GitHub organization access should be represented in the app model and UX. Done means the supported access modes are exposed through the API and the single-provider limitation, if real, is enforced clearly.

Written by the indexing model from the issue text.