Avoid eager loading of wasm binaries when executing a function call

[bowenwang1996]

In execute_function_call, we always first load the wasm binary

nearcore/runtime/runtime/src/actions.rs

Line 82 in a1cac91

let code = match get_contract_code(&runtime_ext, account, apply_state.current_protocol_version)

. However, this step is only needed if the contract has not been compiled. We should refactor to avoid unnecessarily loading of wasm binaries.

[nagisa]

This can be pretty difficult to achieve however. The ContractCode that we're loading here besides the wasm code itself also contains a CryptoHash which is the key into the compiled contract cache.

The obvious thing to do would be to split them up into independent columns perhaps? Or independent key-values within this column? RocksDB does return memory slices that we don't need to copy necessarily, but I believe that the data still needs to be read from the disk and decompressed in full before this slice gets passed to the caller.

[bowenwang1996]

@nagisa contract hash is stored as part of Account, which is readily available in execute_function_call