Add feature to expose IIS hosting details

[twsouthwick]

Adds IIISEnvironmentFeature to expose IIS hosting details. This makes the following changes:

• Updates aspnetcorev2.dll to set environment variables for IIS values we need
• Surfaces IIISEnvironmentFeature via IServer.Features on IIS if the values are available

Fixes #43632

[Tratcher]

@adityamandaleeka, @BrennanConroy, can you check the native code and merge?

[BrennanConroy]

Can we add a test?
This looks similar to what we would add:

aspnetcore/src/Servers/IIS/IIS/test/Common.FunctionalTests/RequestResponseTests.cs

Line 605 in 9402bfa

public async Task HostingEnvironmentIsCorrect()

[BrennanConroy]

Thanks for the test 👍
Now you just need to make it work for both IISExpress and IIS 😉

[adityamandaleeka]

Native parts look fine to me. Maybe a bit too much auto but I'll live... 😆

[twsouthwick]

@BrennanConroy got it working for both IISExpress and IIS. Had to surface some data from the deployer to be able to test the resulting values

@adityamandaleeka I've replaced auto with the types - no preference on my side, so I'll go with yours :)

[adityamandaleeka]

Thanks @twsouthwick

[twsouthwick]

/backport to release/8.0

[ghost]

Hi @twsouthwick. It looks like you just commented on a closed PR. The team will most probably miss it. If you'd like to bring something important up to their attention, consider filing a new issue and add enough details to build context.

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/aspnetcore/actions/runs/6030166080