[contracts] make ProxyFactory build reproducible across machines

[ldct]

TDL

• check that with these changes, two developers with different usernames have the same output after yarn build of ProxyFactory.json::evm.bytecode
• manually deploy ProxyFactory.json::evm.bytecode to testnets
• check that proxyCreationCode on testnets matches Proxy.bytecode that yarn build generates
• edit 42.json, etc to the newly-deployed address
• bump versions of contracts and node so that the new 42.json is picked up