gluon-wan-dnsmasq: rewrite initfile to use procd (#2991)

Rewrite the gluon-wan-dnsmasq initfile to use procd. This allows for
configuring restart handling by procd in case of a crash.

While at it, disable the caching feature optionally used for the regular
dnsmasq on the wan dnsmasq. This daemon is only for redirecting DNS
requests to use local network resolvers, not introducing caching.

Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 64a9478ab8f625ca73e94eb6450712b1cdef007f)

Co-authored-by: David Bauer <mail@david-bauer.net>