Not charge gas for contract dependency loading

[codchen]

Describe your changes and provide context

Since the number of times and timing of contract dependency loading can be different across nodes due to issues like process restart, transaction parallelization, etc., we decide to not charge gas for times when the dependencies need to be loaded from the store, so that the difference wouldn't cause non-determinism.

Using an infinite gas meter instead of the original gas meter + refund because we don't want this now "free" operation to cause panics (e.g. when the original meter is just about to run out of gas)

Testing performed to validate your change

unit tests + load test