misc: print hash as an hex string in logs

[undercover-cactus]

In this PR we improve logs so it would print hash as hex string. It will help with readability and keep consistent how we represent file key value or fingerprint in other places (like in polkadotjs).

It will also help in integration testing when waiting for docker logs to validate behaviors.

Before :

File upload complete. Peer PeerId("12D3KooWSUvz8QM5X4tfAaSLErAZjR2puojo16pULBHyqTMGKtNV") has the entire file Fingerprint([43, 131, 185, 114, 230, 63, 82, 171, 192, 212, 20, 108, 74, 238, 31, 30, 200, 170, 142, 39, 77, 42, 209, 182, 38, 82, 148, 70, 218, 147, 115, 108])

After :

File upload complete. Peer PeerId("12D3KooWSUvz8QM5X4tfAaSLErAZjR2puojo16pULBHyqTMGKtNV") has the entire file 0x2b83b972e63f52abc0d4146c4aee1f1ec8aa8e274d2ad1b626529446da93736c

[snowmead]

Nice improvement!