Unnecessarily large dependency

[tomtau]

Rosetta Go SDK depends on go-ethereum: https://github.com/coinbase/rosetta-sdk-go/blob/9ba330f0a51ab41c1c8738a040eb2b28894b82d9/go.mod#L13 which is a fairly large dependency.
The only thing used from go-ethereum appears to be secp256k1 signing: https://github.com/coinbase/rosetta-sdk-go/blob/9ba330f0a51ab41c1c8738a040eb2b28894b82d9/keys/signer_secp256k1.go#L21

[tac0turtle]

want to echo this, the core parts of the Rosettas-sdk-go should live separate from custom implementations as the core part is a dependency for projects not housed in here.

[tac0turtle]

@tomtau we will maintain a stripped version of essential items here https://github.com/cosmos/rosetta-sdk-go. I opened a pr with only the items that are required as dependencies

[chappjc]

It's also worth noting that the code in go-ethereum/crypto (no-cgo version) uses "github.com/btcsuite/btcd/btcec/v2", which is actually a rather thin wrapper around "github.com/decred/dcrd/dcrec/secp256k1/v4".

e.g. go-libp2p was recently update to go straight to the source for secp256k1 with no unneeded dependencies: libp2p/go-libp2p#1689

Going pure-Go (dropping cgo) might actually be a win for rosetta-sdk-go in terms of simplifying the build toolchain and gaining reproducible binaries.