test: protobuf vectors for reactors (#5221)

## Description

Add test vectors for all reactors

- [x] state-sync
- [x] privval
- [x] mempool
- [x] p2p
- [x] evidence
- [ ] light?

this PR is primarily oriented at testvectors for things going over the wire. should we expand the testvectors into types as well?

Closes: #XXX

statesync/messages_test.go

@@ -1,6 +1,7 @@
 package statesync
 
 import (
+	"encoding/hex"
 	"testing"
 
 	"github.com/gogo/protobuf/proto"
@@ -81,3 +82,26 @@ func TestValidateMsg(t *testing.T) {
 		})
 	}
 }
+
+//nolint:lll // ignore line length
+func TestStateSyncVectors(t *testing.T) {
+
+	testCases := []struct {
+		testName string
+		msg      proto.Message
+		expBytes string
+	}{
+		{"SnapshotsRequest", &ssproto.SnapshotsRequest{}, "0a00"},
+		{"SnapshotsResponse", &ssproto.SnapshotsResponse{Height: 1, Format: 2, Chunks: 3, Hash: []byte("chuck hash"), Metadata: []byte("snapshot metadata")}, "1225080110021803220a636875636b20686173682a11736e617073686f74206d65746164617461"},
+		{"ChunkRequest", &ssproto.ChunkRequest{Height: 1, Format: 2, Index: 3}, "1a06080110021803"},
+		{"ChunkResponse", &ssproto.ChunkResponse{Height: 1, Format: 2, Index: 3, Chunk: []byte("it's a chunk")}, "2214080110021803220c697427732061206368756e6b"},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+
+		bz := mustEncodeMsg(tc.msg)
+
+		require.Equal(t, tc.expBytes, hex.EncodeToString(bz), tc.testName)
+	}
+}