Support for source port and destination port on routing policy

[Quentin Smith]

systemd-networkd exposes these as SourcePort and DestinationPort in the [RoutingPolicyRule] section.

While we're at it, there appear to be several other matchers that are missing as well.

Documented fields in netplan:
from
to
table
priority
mark
type-of-service

and the missing fields are:
IncomingInterface
OutgoingInterface
SourcePort
DestinationPort
IPProtocol
InvertRule
Family
User
SuppressPrefixLength
Type

Filtering by port number allows certain bandwidth-hungry applications to be sent on a different interface in dual-homed scenarios.