feat: FeeDecorator

[inon-man]

Description

This PR adds a new Ante handler FeeDecorator that merges TaxFeeDecorator, BurnTaxFeeDecorator, and DeductFeeDecorator of CosmosSDK. This is required for allowing validators to submit oracle vote transactions without fee.

Closes: #330

[nghuyenthevinh2000]

@inon-man I think it needs one more oracle submit tx test to make sure. Let's me add that one in

[fragwuerdig]

One question. Does this FeeDecorator deduct the taxes from the account balance rather than deducting it from the fee field of the tx. Did I read that correctly?

[nghuyenthevinh2000]

One question. Does this FeeDecorator deduct the taxes from the account balance rather than deducting it from the fee field of the tx. Did I read that correctly?

fee is collected first from account to FeeCollector, then tax is get from FeeCollector

[StrathCole]

Does this fully solve the calculation issues e.g. in terms of simulate endpoint requests? What effect does it have for contracts?

[nghuyenthevinh2000]

@inon-man please check again before merge. I am all good.

[inon-man]

Does this fully solve the calculation issues e.g. in terms of simulate endpoint requests? What effect does it have for contracts?

You can think this as a refactoring task. It does not change the behavior of the chain of Ante handlers. I migrated all the tests as well.

[inon-man]

One question. Does this FeeDecorator deduct the taxes from the account balance rather than deducting it from the fee field of the tx. Did I read that correctly?

In addition, DeductFee function sends fees from account to fee collector.