This changes the definitions of Ping and Pong, adding an optional field
for the sequence number. This field was previously encoded/decoded using
the "tail" struct tag, but using "optional" is much nicer.
see https://github.com/ethereum/go-ethereum/pull/22842
Co-authored-by: Felix Lange <fjl@twurst.com>
Encode and hash logic was duplicated in multiple places.
* Move encoding to p2p/discover/v4wire
* Move hashing to p2p/enode/idscheme
* Change newRandomLookup to create a proper random key on a curve.
This moves all v4 protocol definitions to a new package, p2p/discover/v4wire.
The new package will be used for low-level protocol tests.
# Conflicts:
# p2p/discover/v4_lookup_test.go
# p2p/discover/v4_udp.go
# p2p/discover/v4_udp_test.go
