tools: ynl: generate code for rt-addr and add a sample

YNL C can now generate code for simple classic netlink families.
Include rt-addr in the Makefile for generation and add a sample.

  $ ./tools/net/ynl/samples/rt-addr
              lo: 127.0.0.1
       wlp0s20f3: 192.168.1.101
              lo: ::
       wlp0s20f3: fe80::6385:be6:746e:8116
            vpn0: fe80::3597:d353:b5a7:66dd

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250410014658.782120-13-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>