zetacore : observer NonceToCCTX mapping is set twice during genesis

[kingpinXD]

• 1NonceToCCTX is set by the crosschain module genesis when saving the CCTX
  https://github.com/zeta-chain/zeta-node/blob/2cd0b73f27167222199341601a1a2f305a149b27/x/crosschain/keeper/cctx.go#L25-L34

• It also gets set again by the observer module during the genesis
  https://github.com/zeta-chain/zeta-node/blob/2cd0b73f27167222199341601a1a2f305a149b27/x/observer/genesis.go#L130-L132

Also, the value should remain the same as the index; the key is generated from the nonceToCCTX object, so setting it twice should be avoided.

[kingpinXD]

Let's consider refactoring the Crosschhain genesis. The state for an module should always be imported by the import function for that specific module , Observer in this case .

We should also avoid using High-level functions such as SaveCCTXUpdate during genesis amd try to keep the format as simple as possible ,
Ideally iterating through the elements and setting them if not empty