Fix code duplication in the newHash

[Mdaiki0730]

Description

From #499
I created this PR because I found a completely different solution than the above.

[codecov]

Codecov Report

Merging #509 (f906760) into main (6c0f491) will increase coverage by 0.11%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #509      +/-   ##
==========================================
+ Coverage   65.46%   65.57%   +0.11%     
==========================================
  Files         278      278              
  Lines       37972    37970       -2     
==========================================
+ Hits        24857    24898      +41     
+ Misses      11309    11269      -40     
+ Partials     1806     1803       -3     

Impacted Files	Coverage Δ
p2p/pex/addrbook.go	71.57% <100.00%> (-0.10%)	⬇️
p2p/switch.go	65.90% <0.00%> (-0.62%)	⬇️
consensus/state.go	73.38% <0.00%> (-0.06%)	⬇️
statesync/syncer.go	82.80% <0.00%> (+0.57%)	⬆️
p2p/pex/pex_reactor.go	79.67% <0.00%> (+0.61%)	⬆️
mempool/reactor.go	79.67% <0.00%> (+1.09%)	⬆️
statesync/snapshots.go	94.96% <0.00%> (+1.25%)	⬆️
blockchain/v0/pool.go	79.58% <0.00%> (+2.58%)	⬆️
privval/socket_listeners.go	83.78% <0.00%> (+4.05%)	⬆️
privval/signer_endpoint.go	76.92% <0.00%> (+4.39%)	⬆️
... and 2 more