Remove outdated GenesisSupplyOffsets from the sdk fork's bank genesis state constructor

[nicolaslara]

Background

The sdk fork is using GenesisSupplyOffsets in the banktypes.NewGenesisState() constructor. This is incompatible with the ibc-go testing package which expects the new signature (https://github.com/cosmos/ibc-go/tree/main/testing).

Suggested Design

~~Remove outdated GenesisSupplyOffsets from the sdk fork and make the necessary changes to both this repo and the sdk fork for the tests to pass~~

Add a new constructor to x/bank's GenesisState that uses offsets and remove the legacy parameter from the default constructor

Acceptance Criteria

• [ ] Tests pass on both repos
• [ ] Someone that understands the genesis state has reviewed the changes (on both repos) to make sure they're ok

[nicolaslara]

This branch has my changes to the osmosis repo for this: https://github.com/osmosis-labs/osmosis/tree/supply-offset-changes-on-sdk-fork

And this one has the changes on the sdk fork: https://github.com/osmosis-labs/cosmos-sdk/pull/312

Thanks to @xBalbinus for fixing one of the tests (https://github.com/osmosis-labs/osmosis/pull/2274) and for @p0mvn for pointing it out to me.