Auto merge of #94857 - petrochenkov:doclink2, r=oli-obk

Resolve documentation links in rustc and store the results in metadata

This PR implements MCP rust-lang/compiler-team#584.

Doc links are now resolved in rustc and stored into metadata, so rustdoc simply retrieves them through a query (local or extern),

Code that is no longer used is removed, and some code that no longer needs to be public is privatized.
The removed code includes resolver cloning, so this PR fixes rust-lang/rust#83761.

Author: bors