Usage of 'Immutable' for variables storing keccak hashes

[0xScratch]

Description

Replaced 'constant' with 'immutable' on the basis of these two links -> 1st and 2nd
This seems more effective.

Tests

No tests added cuz it wasn't necessary!

[codecov]

Codecov Report

Merging #8024 (ce1b1e3) into develop (3e890bb) will increase coverage by 0.07%.
Report is 20 commits behind head on develop.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #8024      +/-   ##
===========================================
+ Coverage    46.01%   46.08%   +0.07%     
===========================================
  Files          170      170              
  Lines         7121     7121              
  Branches      1138     1138              
===========================================
+ Hits          3277     3282       +5     
+ Misses        3717     3712       -5     
  Partials       127      127              

Flag	Coverage Δ
cannon-go-tests	63.47% <ø> (ø)
chain-mon-tests	26.95% <ø> (ø)
common-ts-tests	26.74% <ø> (ø)
contracts-bedrock-tests	40.33% <ø> (+0.17%)	⬆️
contracts-ts-tests	100.00% <ø> (ø)
core-utils-tests	44.03% <ø> (ø)
sdk-next-tests	41.92% <ø> (ø)
sdk-tests	41.92% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...phery/faucet/authmodules/AdminFaucetAuthModule.sol	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

[Inphi]

looks good to me. Unfortunate constant behavior. Thanks for fixing.