Error/warning messages should contain link to documentation about that particular error/warning

[rolfbjarne]

Description

Error/warning messages should contain link to documentation about that particular error/warning.

Ideally format the error message in such a way that the IDEs will open the link.

This affects:

• MSBuild errors/warnings
• dotnet-linker/mtouch/mmp errors/warnings

The first step however is to publish the documentation about these errors and warnings online (it was removed when Xamarin docs were scrubbed).

Ref: #21204.