feat: Add gas per-loop-iteration in ecocredit messages (#519)

[ruhatch]

Description

Add fixed gas cost to ecocredit messages per-loop-iteration

Closes: #519

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[codecov]

Codecov Report

Merging #526 (ba8e3cc) into master (c179d8a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #526   +/-   ##
=======================================
  Coverage   77.51%   77.52%           
=======================================
  Files         100      100           
  Lines       12755    12760    +5     
=======================================
+ Hits         9887     9892    +5     
  Misses       2276     2276           
  Partials      592      592           

Flag	Coverage Δ
experimental-codecov	77.52% <100.00%> (+<0.01%)	⬆️
stable-codecov	68.31% <100.00%> (+0.01%)	⬆️

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[blushi]

Should we also charge some extra gas in isCreatorAllowListed? (it's more or less the same logic in x/authz and x/feegrant)
cc/ @clevinson @ruhatch

[atheeshp]

Should we also charge some extra gas in isCreatorAllowListed? (it's more or less the same logic in x/authz and x/feegrant)
cc/ @clevinson @ruhatch

I think we have to.

[atheeshp]

lgtm

[aleem1314]

LGTM