Convert ShardedHashMap to use hashbrown::HashTable

The `hash_raw_entry` feature has finished fcp-close, so the compiler
should stop using it to allow its removal. Several `Sharded` maps were
using raw entries to avoid re-hashing between shard and map lookup, and
we can do that with `hashbrown::HashTable` instead.

compiler/rustc_data_structures/src/lib.rs

@@ -24,7 +24,6 @@
 #![feature(dropck_eyepatch)]
 #![feature(extend_one)]
 #![feature(file_buffered)]
-#![feature(hash_raw_entry)]
 #![feature(macro_metavar_expr)]
 #![feature(map_try_insert)]
 #![feature(min_specialization)]