Auto merge of #48149 - varkor:generics-generalisation, r=petrochenkov

The Great Generics Generalisation: HIR Edition

This is essentially a followup to https://github.com/rust-lang/rust/pull/45930, consolidating the use of separate lifetime and type vectors into single kinds vectors wherever possible. This is intended to provide more of the groundwork for const generics (https://github.com/rust-lang/rust/issues/44580).

r? @eddyb
cc @yodaldevoid

src/librustdoc/lib.rs

@@ -18,6 +18,7 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(fs_read_write)]
+#![feature(iterator_find_map)]
 #![feature(set_stdio)]
 #![feature(slice_sort_by_cached_key)]
 #![feature(test)]