feat: supports gas payment for two-way calls

[npty]

Description

This PR adds support for nested contract calls. It does this by checking the transaction receipt log for ContractCall or ContractCallWithToken events. If these events are found, the relayer adds a new gas paid event with the deducted gas fee.

Other improvements

• Add typechain to generate types for the GasService and Gateway contracts

Issues

• The deducted gas fee logic doesn't work correctly if there're multiple ContractCall or ContractCallWithToken events. I think we can fix it later because we don't have examples that executes callContract or callContractWithToken multiple times in the destination contract.

How to test against axelar-examples?

1. Clone this branch
2. Run npm install
3. In axelar-examples, run npm install @axelar-network/axelar-local-dev@relative-path-to-axelar-local-dev
4. In axelar-examples, run npm run test

[StephenFluin]

Tested with the latest axelar-examples with the updated sync/ack example, works well!