Minimum GasUsed proportional to GasLimit

[crypto-facs]

Closes: #1085

Description

More info about this issue on the issue, but in summary this PR aims to add a new functionality on which to control the minimum amount of gas to be charged proportional to the GasLimit of the transaction. The equation is the following:

max(gasUsed, gasLimit / MinGasDenominator)

MinGasDenominator being an EVM module param for the minimum about to be charged to be able to be updated as the network changes.

NOTE: This is a breaking change

---

For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

---

For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #1087 (03bbfbc) into main (f06df8c) will increase coverage by 0.01%.
The diff coverage is 73.21%.

❗ Current head 03bbfbc differs from pull request most recent head fc5561f. Consider uploading reports for the commit fc5561f to get more accurate results

@@            Coverage Diff             @@
##             main    #1087      +/-   ##
==========================================
+ Coverage   59.55%   59.57%   +0.01%     
==========================================
  Files          84       85       +1     
  Lines        6933     6971      +38     
==========================================
+ Hits         4129     4153      +24     
- Misses       2591     2601      +10     
- Partials      213      217       +4     

Impacted Files	Coverage Δ
x/evm/keeper/migrations.go	66.66% <0.00%> (-33.34%)	⬇️
x/evm/migrations/v2/migration.go	42.85% <42.85%> (ø)
x/evm/module.go	52.85% <60.00%> (-0.88%)	⬇️
x/evm/types/params.go	93.47% <81.81%> (-6.53%)	⬇️
x/evm/keeper/state_transition.go	75.37% <87.50%> (+0.30%)	⬆️
x/evm/simulation/genesis.go	93.54% <100.00%> (ø)

[danburck]

@crypto-facs LGMT, left minor comments.

Do you think it makes sense to add unit tests here?

[fedekunze]

Thanks @crypto-facs! Changes LGTM. Some things pending:

• tests to check that the multiplier logic works as intended
• update specification
• add migration logic to set the new parameter during upgrade
  • migration 1 -> 2 (consensus version of the evm module)
  • define migrator

[fedekunze]

LGTM, minor change requested