base-files: upgrade: use procd to kill managed daemons

base-files: upgrade: use procd to kill managed daemons

These processes are managed by procd and set to start again when killed
via the procd instance parameter "respawn" being set during init.

Example:
procd_set_param respawn 3600 1 0

When they are killed manually during sysupgrade,
they are started again in 5 seconds or less, depending on
how the "respawn" parameter is set.

Use procd through ubus to disable the instances that respawn them,
however, allow dnsmasq, netifd, and logd to restart for remote logging.

Properly closing all these processes increases free memory by about 3 MB,
which should help low memory devices upgrade without crashing.

For very low memory devices (set to 32 MB for now)
also kill dnsmasq, netifd, and logd for an additional 3 MB of free memory.

Also, bump sleep values to allow at least 10 seconds
for network interfaces and daemons
to come up after they are killed and restarted
before caches are dropped.

Signed-off-by: Michael Pratt <mcpratt@pm.me>