Model macro (#1545)

closes #1060

- remove `*EthAbi` traits, replace with `Encode/Decode<EthAbi>`
- extend `proto` attribute macro added in #1533 to a more generic
`model` macro that allows for ethabi as well as proto
- also does serde and standard derives (i.e. debug, clone, partialeq,
arbitrary)
- since it's an attribute macro we can also just use the derive's
attributes no problem (`#[serde]`, `#[debug]`, etc)
  - yes i totally planned this all along
- definitely not because attribute macros were 1 less feature for syn
that i've now enabled anyways for the custom debug derive
  - 😀
- general cleanup
- yeet `custom_debug_derive` in favour of our own in-house custom debug
derive
  - its better, trust me
- make json encoding a bit more consistent for enums (changes to
`lib/tendermint-verifier/src/test/*.json` can be largely ignored, unless
you really want to stare at some json)