refactor[test]: add some sanity checks to abi_decode tests (#4096)

QOL improvements for abi_decode tests:

- added sanity checks to abi decode tests to ensure that we're never
failing on calldatasize
- also split the creation of payload into two parts when calling target
contract with low-level msg_call to increase readability

---------

Co-authored-by: Charles Cooper <cooper.charles.m@gmail.com>