In preparation for adding a NodeAnnouncement2 struct along with a
NodeAnnouncement interface, this commit renames the existing
NodeAnnouncment struct to NodeAnnouncement1.
Check that the node ann doesnt contain more than 1 DNS addr.
This will ensure that we now start rejecting new node announcements
with multiple DNS addrs since this check is called in the gossiper
before persisting a node ann to our local graph.
It also validates the DNS fields according to BOLT #7 specs.
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.
The `netann` package is a more appropriate place for this code to live.
Also, once the funding transaction code is moved out of the
`graph.Builder`, then no `lnwire` validation will occur in the `graph`
package.
To simplify the message signing API even further, we refactor the
lnwallet.MessageSigner interface to use a key locator instead of the
public key to identify which key should be signed with.
