refactor: clean up old smart contract ABI definitions

[david-bakin-sl]

• AbiConstants is still hanging around, shouldn't be. Only remaining uses are for Ethereum event declarations. (And those are declared extremely opaquely as byte strings.). Find some other place for these event declarations (and a better notation!) and nuke this file.
  • Probably should be in the translator classes with the method declaration - they're used in the *Call and *LoggingUtils classes in the same package as the corresponding *Translator, so in other words: They're local.
• I think it possible there's another such old file hanging around - I have this vague recollection of it but can't find it now. Look for it maybe?
• Consider how some of our translator classes - e.g., CreateTranslator build signatures out of substrings. Some of that is done to have common definnitions of structs and reuse them. But some is just obfuscating, like a + ARRAY_BRACKETS + just for []. Reconsider this.