Rollup merge of #144712 - nnethercote:dedup-num-types, r=fmease

Deduplicate `IntTy`/`UintTy`/`FloatTy`.

There are identical definitions in `rustc_type_ir` and `rustc_ast`. This commit removes them and places a single definition in `rustc_ast_ir`. This requires adding `rust_span` as a dependency of `rustc_ast_ir`, but means a bunch of silly conversion functions can be removed.

r? `@fmease`

Author: jdonszelmann

Cargo.toml

@@ -18,7 +18,9 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 # Provides access to APIs that expose internals of the rust compiler.
 # APIs enabled by this feature are unstable. They can be removed or modified
 # at any point and they are not included in the crate's semantic versioning.
 rustc_internal = []
+# tidy-alphabetical-end