Refactor: use EOS VM's WASM parser with EOS VM OC

[spoonincode]

EOS VM OC needs to be refactored to use EOS VM's WASM parser. This will allow commonality between the two implementations and is probably tech debt number one for EOS VM OC.

This is a carryover of eosnetworkfoundation/mandel#640 however I have dropped the discussion about wholesale removal of WAVM's wasm parser. It's not clear that is the correct approach: prior to CONFIGURABLE_WASM_LIMITS2 I believe WAVM's parser is always clutched in in front of EOS VM's parser. We may want to maintain that behavior indefinitely just to ensure we don't goof up something. Leaving WAVM's parser in the code indefinitely doesn't seem too high overhead.

[spoonincode]

Completely remove WASM::check_limits as part of this, see #969