Allow passing in RPC cache path for Solidity tests

[agostbiro]

Problem

There is no way to pass in custom RPC cache directory path to the Solidity test runner.

Solution

• Remove the no_storage_caching config option.
• Replace it with optional RPC cache path config option. If this is none, then no RPC calls will be cached, otherwise data is cached to <rpc_cache_path>/<chain id>/<block number>.