Drop EEI methods for accessing to contracts' code

[chfast]

Drop:

• codeCopy() https://github.com/ewasm/design/blob/master/eth_interface.md#codecopy
• getCodeSize() https://github.com/ewasm/design/blob/master/eth_interface.md#getcodesize
• externalCodeCopy() https://github.com/ewasm/design/blob/master/eth_interface.md#externalcodecopy
• getExternalCodeSize() https://github.com/ewasm/design/blob/master/eth_interface.md#getexternalcodesize

The externalCodeCopy() and getExternalCodeSize() might still be available in EVM1 compatibility mode.

Access to external code hash might be useful.

[chfast]

Hypothesis: (Not all) nodes would have to keep the original code, they can keep the compiled / optimized code and the hash of the original code.