* Add min_gas_price to feemarket params
* Add MinGasPriceDecorators
* feemarket integration tests for MinGasPrice
* Restructure integration tests
* Simplify integration tests context
We use DeliverTx context to set up the app, otherwise not all settings are initialized.
We test CheckTx with `s.app.BaseApp.CheckTx(req)`, which uses the `CheckTx` mode and context.
* Update MinGasPrice spec in feemarket module
* reorder ethermint module order for initializing genesis
* feemarket migrations for adding MinGasPrice param
* update changelog
* Additional unit tests for MinGasPrice = 0, tx gas price > 0 (PR review)
https://github.com/tharsis/ethermint/pull/1104#discussion_r884991661
* Use 0 MinGasPrice for transaction simulations
* Fix duplicate registration of feemarket GenesisState and Params (PR review)
https://github.com/tharsis/ethermint/pull/1104#issuecomment-1141893712
