Minimise changes to the TNLS-Gateway

[ltfschoen]

The public key of the user that deploys the custom Nunya.Business contract is sent through to the custom EVM Gateway contract so only that user may call that custom EVM Gateway contract, however we actually want to try and use the default EVM Gateway contract that has been deployed by the Secret network team with minimal changes and move the logic to the Secret contract instead. Apart from the creator of the Nunya.Business contract, the only other users that call any Secret network functions are accounts whose public keys are provided by the creator of the Nunya.Business giving those accounts permission to call the withdraw function.

Also consider using the TNLS-Gateway from https://github.com/ltfschoen/SecretPath/blob/main/TNLS-Gateways/public-gateway/src/Gateway.sol since that template is in the same repo as the Relayer that we're using via Git Submodules, and migrate our changes across to that, although it might be necessary to use symlinks for deployment and unnecessary complexity