feat(2.11): burn fees

[emidev98]

This pull request, introduce a new module named x/feeburn with very specific scope: the proportional amount of gas fees that are not used by the validator to comput the transaction will be burn. The module also has a parameter which defines if the burning mechanism is enabled or disabled.

In the x/feeburn post handler it will check if the module is enabled, if the transaction fees are defined, if there is a limit for the gas and will use the gas meter to calculate what is the proportional amount of tokens to be burned with the following formula:

unusedFees = truncate((remainingGas / gasLimit) * amountOfFeeTokens) 

this formula applies to all the tokens from the transaction fee

The reasoning behind this implementation is that the user already paid for the full gas (gas_limit) but the validator didn't consumed all the gas to reach the limit, which makes it unfair to give the full amount of tokens to the validators.

At the same time will make it unfair to give the tokens back to the user because the user was already willing to spend that amount of tokens and by giving them back none will be responsible with the gas_limit, everyone will have the incentive to chose the maximum gas limit since the non-used gas-fee will be returned to them.

[codecov]

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