Document reserved aliases

[GangWang01]

Problem

#5198

Solution

Add doc for reserved aliases since .NET 7.0, as well as reference for dotnetcli.host.json.
Add unit tests dotnet/sdk#28748

Checks:

• Added unit tests
• Added #nullable enable to all the modified files ?

[vlada-shubina]

Looks good. Let's improve this article to explain dotnetcli host file format in first place. Please let me know if you'd like to do it or I can do it.

Example of it can be found here: https://github.com/dotnet/sdk/blob/main/template_feed/Microsoft.DotNet.Common.ProjectTemplates.7.0/content/ClassLibrary-CSharp/.template.config/dotnetcli.host.json

It allows the following:

• symbolsInfo: objects should match the name of parameter symbol in template.json
  • override short and long alias for parameter symbol. In case "shortName": "" it means that short alias should not be used.
  • hide parameters in CLI (isHidden property)
• usageExamples - currently not used - Utilize 'usageExamples' from dotnetcli.host.json #3262

Also it would be good to have unit/integration tests on it. Help tests test it in away though. We do have some unit tests here: https://github.com/dotnet/sdk/blob/main/src/Tests/Microsoft.TemplateEngine.Cli.UnitTests/HostDataLoaderTests.cs

[GangWang01]

I'd like to dive into host file and improve this article as well as tests.

[JanKrivanek]

Very nice and valuable overview! Looking forward the addition of host files parameters altering functionality

[vlada-shubina]

Generally looks good, suggesting some changes below.

[vlada-shubina]

Added couple of suggestions.

[vlada-shubina]

Thanks