Rollup merge of #37498 - sanxiyn:unused-type-alias, r=eddyb

Remove unused type aliases

Found by extending the dead code lint. The lint itself is work in progress because of false positives.

cc #37455.

diff --cc src/librustc_borrowck/borrowck/mod.rs
Simple merge

diff --cc src/libstd/collections/hash/table.rs
Simple merge