Improve and add more tests to CCTX validation functions

[lumtis]

Describe the Issue

The validation for inbound and outbound: https://github.com/zeta-chain/node/blob/develop/x/crosschain/types/validate.go

There are some issues like reported here: https://github.com/zeta-chain/node/issues/2228

The unit tests must be extended to cover any kind of CCTXs, from any chains.

Some checks are too opiniated like checking ballot index: not all inbounds will be validated through ballots in the future.