Log string header_hash on long validation warnings

[hoffmang9]

Purpose:

We are logging the binary form of the header hash in the "WARNING Block validation time" is slow log entry. Instead log the human readable header hash.

Current Behavior:

Slow look up warning log looks like this:

2024-01-11T14:44:13.647 full_node chia.full_node.full_node: WARNING  Block validation time: 11.09 seconds, pre_validation time: 1.68 seconds, post-process time: 6.97 seconds, cost: 5462045750, percent full: 49.655% header_hash: b'\xd5\x96\xc8\x10\xb4\x93Y\x82\xf8\x99H:G\x99\xe7E\x86\x02\xaa\x97q\x868\x1fO\x97Pe\xfd27\x95' height: 4787397

New Behavior:

Now these will be human readable and searchable:

2024-01-11T14:44:13.647 full_node chia.full_node.full_node: WARNING  Block validation time: 11.09 seconds, pre_validation time: 1.68 seconds, post-process time: 6.97 seconds, cost: 5462045750, percent full: 49.655% header_hash: d596c810b4935982f899483a4799e7458602aa977186381f4f975065fd323795 height: 4787397

Testing Notes:

[hoffmang9]

Testing found the object still contained a bytes string so now using header_hash.hex() to get the correct human readable method.

Please squash when merging.

[arvidn]

that was my mistake