rpc: replace Amino with new JSON encoder (#4968)

Migrates the `rpc` package to use new JSON encoder in #4955. Branched off of that PR.

Tests pass, but I haven't done any manual testing beyond that. This should be handled as part of broader 0.34 testing.

crypto/ed25519/ed25519.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/tendermint/tendermint/crypto"
 	"github.com/tendermint/tendermint/crypto/tmhash"
+	tmjson "github.com/tendermint/tendermint/libs/json"
 )
 
 //-------------------------------------
@@ -31,6 +32,11 @@ const (
 	SeedSize = 32
 )
 
+func init() {
+	tmjson.RegisterType(PubKey{}, PubKeyAminoName)
+	tmjson.RegisterType(PrivKey{}, PrivKeyAminoName)
+}
+
 // PrivKey implements crypto.PrivKey.
 type PrivKey []byte