Add reporting of long wake locks.

These appear as a new event in the battery stats history,
"longwake" in the long version and "Elw" in the checkin.

The power manager keeps track of which wake locks are held
for a long time and reports them to battery stats.  Long
is currently considered 1 minute or more.  Once it is long,
the start event will appear, and once if is released the
event will end.

In the case of a wake lock changing (typically its work
source changing), for purposes of this accounting this is
considering a pure release of the old state and start of
the new state...  so the timer will reset back to one
minute until the wake lock is considered long.  This is done
to prevent things that make lots of changes to wake lock
work sources from spamming the log.

Bug: 28753137

Change-Id: I33b6168c57a7ea6ea558273dec731704123124a5