kmod-sched-cake: drop out of tree package, use kernel version

kmod-sched-cake: drop out of tree package, use kernel version

CAKE made it to kernel 4.19 and since OpenWrt now at kernel 4.19 we can
drop the out of tree cake package in base repository.

Add kmod-sched-cake to netsupport so package dependencies are still met.
Similarly CAKE is retained as an optional qdisc module to avoid base
scheduler package size implications.

Backport upstream patches from k5.1 to address some small bugs and
support fwmark usage.

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>