Simplify the artifact category mechanism in PublishArtifactsInManifest task

[riarenas]

The current approach of keeping a static mapping of extension -> category

arcade/src/Microsoft.DotNet.Build.Tasks.Feed/src/PublishArtifactsInManifest.cs

Lines 897 to 909 in 316c80d

	var whichCategory = new Dictionary<string, string>()
	{
	{ ".NUPKG", "NETCORE" },
	{ ".PKG", "OSX" },
	{ ".DEB", "DEB" },
	{ ".RPM", "RPM" },
	{ ".NPM", "NODE" },
	{ ".ZIP", "BINARYLAYOUT" },
	{ ".MSI", "INSTALLER" },
	{ ".SHA", "CHECKSUM" },
	{ ".POM", "MAVEN" },
	{ ".VSIX", "VSIX" },
	};

means that whenever we need to add or change these categories, we need to:

• Generate a new version of the task package
• Change the version files of the Arcade SDK to use the new task package

The process is not great whenever a new extension needs to be added.

A possible solution is to simplify the categories into:

• Packages (NuGet packages)
• Blobs (Everything else)
• Hybrid (Blobs that are also packages, such as symbol packages)

[mmitche]

Not needed for 3.1, moving to 5

[riarenas]

Fits the theme of improvements that we want to make for .NET 5. Keeping in the current epic.