Describe the Issue

MsgUpdateChainInfo currently requires providing the entire structureand replace the entire structure in the store. This current workflow can have a risk or removing or changing existing chains

We should update the message to allow only providing a single chain and prevent making mistakes

In addition, we need to add a new message to remove an existing chain

### Tasks
- [ ] Add new admin authorization MsgRemoveChainInfo on Testnet
- [ ] Add new admin authorization MsgRemoveChainInfo on Mainnet