Auto merge of #82183 - michaelwoerister:lazier-defpathhash-loading2, r=wesleywiser

Simplify lazy DefPathHash decoding by using an on-disk hash table.

This PR simplifies the logic around mapping `DefPathHash` values encountered during incremental compilation to valid `DefId`s in the current session. It is able to do so by using an on-disk hash table encoding that allows for looking up values directly, i.e. without deserializing the entire table.

The main simplification comes from not having to keep track of `DefPathHashes` being used during the compilation session.

diff --cc Cargo.lock
Simple merge