crypto: provide simple way to add new curves

[tac0turtle]

Feature Request

Summary

currently there is not a way to add new curves to comet unless you fork the software. This causes many forks for simple changes.

Problem Definition

adding new curves forces users to fork the software. (unless im missing something)

Proposal

add simple way to add new curves to be used for consensus key signing

Zondax is proposing an api to help with this in the sdk. we could look at hosting the new api in its own module to enable usage in comet as well

Tasks

Beta Give feedback

1. Ping Filipo for code check of feat(proto)!: replace PubKey in abci.ValidatorUpdate with PubKeyType and PubKeyBytes #2843
2. open folluw-up issue to capture the "fully modular support of registering new curvers"

[tac0turtle]

to add on it would be nice to have the file system privval also take arbitrary curves. This way users dont also have to fork privval file once pluggable curves land

relevant tendermint/tendermint#5603 but allowing the node instanciator to set the underlying curve would be one step better than the issue linked

[cason]

I think we would need a method such as RegisterKey at some place.

Now one can implement the crypto.PrivKey and crypto.PrivKey interfaces, but not sure how to set the new key for use by Comet.

[tac0turtle]

i think the pubkey proto type may need some changing as the current design wouldnt allow register key without redoing the proto types

[melekes]

refs #2399