Remove unused dependencies and methods

[mds1]

Closes #152

(branched off #151, so figured we can just merge this into 151's branch first since this will be a much quicker PR to review/merge)

[paulmillr]

seems like this doesn't help much judging from lockfile.

Well, since ethers.js wants to include noble in the next version (ethers-io/ethers.js#727, twitter), I think you'll see the real pkg size difference right after that.

[mds1]

Yea ended up being a small change. Since it's a monorepo, a good portion of the lockfile comes from dependencies of the fronted + contracts workspaces too, so elliptic and it's dependencies likely won't be removed from lockfile anytime soon. But they still should be tree-shaken out of the production umbra-js bundle, though I haven't looked into that yet

[apbendi]

lgtm!