Hash calculation based on proto.Structs

[antho1404]

With the migration to proto.structs instead of map[string]interface{} the hash calculation doesn't work anymore.

If an event has exactly the same instanceHash and eventKey but different data, the generated hash will be exactly the same which is wrong. We should have different hash.

This problem should also apply to the execution and its inputs

To reproduce:

package event

import (
	"testing"

	"github.com/gogo/protobuf/types"
	"github.com/mesg-foundation/engine/hash"
	"github.com/stretchr/testify/require"
)

func TestHashEvent(t *testing.T) {
	e1 := Create(hash.Int(0), "-", &types.Struct{
		Fields: map[string]*types.Value{
			"foo": &types.Value{
				Kind: &types.Value_StringValue{
					StringValue: "bar",
				},
			},
		},
	})
	e2 := Create(hash.Int(0), "-", &types.Struct{
		Fields: map[string]*types.Value{
			"foo": &types.Value{
				Kind: &types.Value_StringValue{
					StringValue: "bar2",
				},
			},
		},
	})
	require.NotEqual(t, e1.Hash, e2.Hash)
}