Microsoft.Extensions.ApiDescription.Server does not dispose the created host thus could hang/fail the build process

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the bug

ApiDescription.Server constructs a service provider by running parts of the application (up to building the `IHost`), then uses this service provider to retrieve API descriptions. However this host and/or service provider is not disposed properly. This is problematic for services that allocate some background resources and are realized as part of building/configuring the host, typically a logger provider.

### Expected Behavior

Generating the OpenAPI doc should not hang or fail.

### Steps To Reproduce

The following example creates a logger provider that starts a worker thread. This is similar to what `ConsoleLoggerProvider` does in https://github.com/dotnet/runtime/tree/v6.0.8/src/libraries/Microsoft.Extensions.Logging.Console/src/ConsoleLoggerProcessor.cs#L30. In this example the thread is not marked as a background thread in order to enforce graceful shutdown.

a.csproj

```csproj

net6.0
enable
enable
true

```

Program.cs

```cs
using Microsoft.Extensions.DependencyInjection.Extensions;

var builder = WebApplication.CreateBuilder(args);

// An instance of this is created when an ILogger is injected to the IHost on .Build()
builder.Logging.Services.TryAddEnumerable(ServiceDescriptor.Singleton());

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();
app.Run();

class DisposeMe : ILoggerProvider
{
private readonly Thread _worker;
private readonly CancellationTokenSource _workerStop = new();
public DisposeMe()
{
Console.WriteLine("I have been constructed");
_worker = new Thread(() => _workerStop.Token.WaitHandle.WaitOne());
// Uncomment for ungraceful shutdown. ConsoleLoggerProvider does this.
// _worker.IsBackground = true;
_worker.Start();
}
public void Dispose()
{
// Flush cache, etc
Console.WriteLine("I have been disposed");
_workerStop.Cancel();
_worker.Join();
}

public ILogger CreateLogger(string categoryName) => Microsoft.Extensions.Logging.Abstractions.NullLogger.Instance;
}
```

Run `dotnet build`. After emitting the openapi doc the build process will hang for 2 minutes then fail.

ApiDescriptions.Server constructs a partial application by throwing after the host is built: https://github.com/dotnet/runtime/blob/v6.0.8/src/libraries/Microsoft.Extensions.HostFactoryResolver/src/HostFactoryResolver.cs#L344
This exception is swallowed at https://github.com/dotnet/runtime/blob/55fb7ef977e7d120dc12f0960edcff0739d7ee0e/src/libraries/Microsoft.Extensions.HostFactoryResolver/src/HostFactoryResolver.cs#L252
The process then fails to quit because the worker thread is still running.

If running the app directly the `app.Run()` call would dispose the host or an exception would crash the entire process.

### Exceptions (if any)

(removed some clutter)
```
Microsoft.Extensions.ApiDescription.Server.targets(66,5): error :
System.TimeoutException: Process C:\Program Files\dotnet\dotnet.exe timed out after 2 minutes.
at Microsoft.Extensions.ApiDescription.Tool.Exe.Run(String executable, IReadOnlyList`1 args, IReporter reporter, String workingDirectory, Boolean interceptOutput)
at Microsoft.Extensions.ApiDescription.Tool.Commands.InvokeCommand.Execute()
at Microsoft.Extensions.ApiDescription.Tool.Commands.CommandBase.<>c__DisplayClass14_0.b__0()
at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[]args)
at Microsoft.Extensions.ApiDescription.Tool.ProgramBase.Run(String[] args, CommandBase command, Boolean throwOnUnexpectedArg)

Microsoft.Extensions.ApiDescription.Server.targets(66,5): error MSB3073:
The command "dotnet "****\../tools/dotnet-getdocument.dll" --assembly "***\bin\Debug\net6.0\a.dll" --file-list "obj\a.OpenApiFiles.cache" --framework ".NETCoreApp,Version=v6.0" --output "obj" --project "a" --assets-file "****\obj\project.assets.json" --platform "AnyCPU" " exited with code 1.
```

### .NET Version

6.0.400

### Anything else?

Some related issues:
#14410 assumptions about the user code that runs as part of the API discovery are still not documented
#23033 some current configuration APIs simply don't support deferring actual work past the host startup.
#43391 the host is intercepted before all user code that affects the API had a chance to run

Some considerations on how to resolve this

**1. Don't run user code. Ever.**
Ideally no user code should be run as part of the build process. This would be bordering on the impossible with the current API shape.

**2. Allow the host to be fully constructed and disposed by user code**
A possible solution (that would also solve #43391) is to capture the host right before starting it. This would allow using this pattern in user code to dispose the host:

**3. Pass a different environment**
The generator should pass `--environment GeneratingApi` or something similar to the app when generating the API doc so that user code could trim unnecessary/dangerous services and configuration. Maybe even make the host refuse to start or immediately quit when this parameter is present.
This is probably the easiest to implement.

```c#
await using var app = builder.Build(); // Currently this would throw an exception before assigning to the variable
// ...
await app.StartAsync();
await app.WaitForShutdownAsync();
```
However this would have the drawback that even more services with side effects could be realized when configuring the pipeline.

dotnet --info

```
.NET SDK (reflecting any global.json):
Version: 6.0.400
Commit: 7771abd614

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19044
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.400\

Host:
Version: 7.0.0-preview.7.22375.6
Architecture: x64
Commit: eecb028078

.NET SDKs installed:
6.0.400 [C:\Program Files\dotnet\sdk]
7.0.100-preview.7.22377.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.0-preview.7.22376.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0-preview.7.22375.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.0-preview.7.22377.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
arm64 [C:\Program Files\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\arm64\InstallLocation]
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set
```