Simplify compact_hash_table implementation
Simplify compact_hash_table implementation

Instead of a separate implementation for find/insert, use just one that
can do both. This reduces the code size and simplifies code coverage;
the resulting code is close to what we had in terms of performance and
since hash table is a fall back should not affect any real workloads.

zeux/pugixml,zeux/pugixml,zeux/pugixml,zeux/pugixml