Auto merge of #76955 - jyn514:refactor-diagnostics, r=euclio

Refactor and fix intra-doc link diagnostics, and fix links to primitives

Closes https://github.com/rust-lang/rust/issues/76925, closes https://github.com/rust-lang/rust/issues/76693, closes https://github.com/rust-lang/rust/issues/76692.

Originally I only meant to fix #76925. But the hack with `has_primitive` was so bad it was easier to fix the primitive issues than to try and work around it.

Note that this still has one bug: `std::primitive::i32::MAX` does not resolve. However, this fixes the ICE so I'm fine with fixing the link in a later PR.

This is part of a series of refactors to make #76467 possible.

This is best reviewed commit-by-commit; it has detailed commit messages.

r? `@euclio`

compiler/rustc_hir/src/hir.rs

@@ -2004,6 +2004,30 @@ pub enum PrimTy {
     Char,
 }
 
+impl PrimTy {
+    pub fn name_str(self) -> &'static str {
+        match self {
+            PrimTy::Int(i) => i.name_str(),
+            PrimTy::Uint(u) => u.name_str(),
+            PrimTy::Float(f) => f.name_str(),
+            PrimTy::Str => "str",
+            PrimTy::Bool => "bool",
+            PrimTy::Char => "char",
+        }
+    }
+
+    pub fn name(self) -> Symbol {
+        match self {
+            PrimTy::Int(i) => i.name(),
+            PrimTy::Uint(u) => u.name(),
+            PrimTy::Float(f) => f.name(),
+            PrimTy::Str => sym::str,
+            PrimTy::Bool => sym::bool,
+            PrimTy::Char => sym::char,
+        }
+    }
+}
+
 #[derive(Debug, HashStable_Generic)]
 pub struct BareFnTy<'hir> {
     pub unsafety: Unsafety,