luci-app-attendedsysupgrade: update status keys and messages

luci-app-attendedsysupgrade: update status keys and messages

The reported status values have changed on the ASU server several
times since the 'steps' list has been updated, so update it to
include all possible values.  Although some of the values in the
list are no longer presented by the official OpenWrt ASU server, they
may still be produced by other ASU servers, so leave them in for now.

Percentages have been adjusted based up on measurement of the build
phases for several build configurations (ath79 vs x86, few packages
vs many...).  The numbers are still (very) rough estimates, but
are more representative than the old values.

Signed-off-by: Eric Fahlgren <ericfahlgren@gmail.com>