Auto merge of #83875 - jyn514:diag_info, r=bugadani

rustdoc: Use DiagnosticInfo in more parts of intra-doc links

This makes the code a lot less verbose.

This is separated into lots of tiny commits because it was easier for me that way, but the overall diff isn't that big if you want to read it at once.

r? `@bugadani`

Author: bors