Update RequiresPreviewFeatures attribute

[pgovind]

Updates RequiresPreviewFeatures attribute with an optional string message and URL

Fixes #56498

cc @jeffhandley @terrajobst

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Updates RequiresPreviewFeatures attribute with an optional string message and URL

Fixes #56498

cc @jeffhandley @terrajobst

Author:	pgovind
Assignees:	-
Labels:	area-System.Runtime
Milestone:	-

[pgovind]

Fix input string

[stephentoub]

Suggested change

	var attribute = new RequiresPreviewFeaturesAttribute(message) {};
	var attribute = new RequiresPreviewFeaturesAttribute(message);

[stephentoub]

Thanks.

[pgovind]

Unrelated build failures. Merging. Thanks for the reviews!!

[JamesNK]

Hi, can the ASP.NET Core repo be updated to use the message immediately? Will it just work once the runtime changes flow into aspnetcore and aspnetcore includes a message, or does it also require other changes in VS or the compiler for the message to show up when building?