Resolve documentation links in rustc and store the results in metadata

This commit implements MCP https://github.com/rust-lang/compiler-team/issues/584

It also removes code that is no longer used, and that includes code cloning resolver, so issue #83761 is fixed.

compiler/rustc_middle/src/arena.rs

@@ -113,6 +113,7 @@ macro_rules! arena_types {
             [decode] trait_impl_trait_tys: rustc_data_structures::fx::FxHashMap<rustc_hir::def_id::DefId, rustc_middle::ty::Ty<'tcx>>,
             [] bit_set_u32: rustc_index::bit_set::BitSet<u32>,
             [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<'tcx>,
+            [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
         ]);
     )
 }