crypto: add in secp256k1 support (#5500)

Secp256k1 was removed in the protobuf migration, this pr adds it back in order to provide this functionality for users (band)

Closes: #5495

go.mod

@@ -6,6 +6,8 @@ require (
 	github.com/BurntSushi/toml v0.3.1
 	github.com/ChainSafe/go-schnorrkel v0.0.0-20200405005733-88cbf1b4c40d
 	github.com/Workiva/go-datastructures v1.0.52
+	github.com/btcsuite/btcd v0.21.0-beta
+	github.com/btcsuite/btcutil v1.0.2
 	github.com/confio/ics23/go v0.0.0-20200817220745-f173e6211efb
 	github.com/cosmos/iavl v0.15.0-rc3.0.20201009144442-230e9bdf52cd
 	github.com/fortytw2/leaktest v1.3.0
@@ -16,6 +18,7 @@ require (
 	github.com/gorilla/websocket v1.4.2
 	github.com/gtank/merlin v0.1.1
 	github.com/libp2p/go-buffer-pool v0.0.2
+	github.com/magiconair/properties v1.8.1
 	github.com/minio/highwayhash v1.0.1
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.7.1