Introduce baseline types required to implement validator set updates

[sug0]

Implements the second item of issue #242

[sug0]

I haven't added unit tests to these yet. I might leave that to the next PR (PrepareProposal), since I'll write the validation code then. idk, what do you think?

[james-chf]

There is one more Cargo.lock - make -C wasm_for_tests/wasm_source check - not currently compiling* for me, though I think there might be something odd with my set up as this type definitely exists

error[E0432]: unresolved import `crate::types::transaction::protocol::ProtocolTxType`
 --> /opt/workspace/heliax/repos/anoma-review/shared/src/types/vote_extensions.rs:7:5
  |
7 | use crate::types::transaction::protocol::ProtocolTxType;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `ProtocolTxType` in `types::transaction::protocol`

For more information about this error, try `rustc --explain E0432`.

[batconjurer]

LGTM!

[james-chf]

It'd be good if we could bound S here (if it's possible?) so that it's impossible to construct a Signed with an invalid tag, something like

pub struct Signed<T, S: SignedSerialize<T> = SerializeWithBorsh>

[sug0]

we already tighten Signed at the impl block starting on line 148. you can only verify signatures of Signed instances with a tag which implements SignedSerialize. you can't use the struct itself to instantiate new values, since it has a private field, but you can use Signed::new_from instead. regardless, we hit the same wall, this instance can't do jack if S does not implement SignedSerialize.

tl;dr I don't think this is an issue