In preparation for adding a NodeAnnouncement2 struct along with a
NodeAnnouncement interface, this commit renames the existing
NodeAnnouncment struct to NodeAnnouncement1.
Replace all usages of the "github.com/go-errors/errors" and
"github.com/pkg/errors" packages with the standard lib's "errors"
package. This ensures that error wrapping and `errors.Is` checks will
work as expected.