Tell activity metrics logger whether a new activity is created

That helps to distinguish hot/warm launch more accurately. In most
cases it was no problem because the previous foreground activity
needs to be pause first so the activity won't attach to process
when executing the launch request. But if all activities are
already paused and the launching activity can be resumed directly,
ATS#realStartActivityLocked will be called immediately so the
transition type becomes always hot launch. E.g. launch activity
which can occlude keyguard from lockscreen.

Also removed unused ActivityStarter#startResolvedActivity.

Bug: 186692122
Test: ActivityMetricsLoggerTests
      ActivityMetricsLaunchObserverTests

Change-Id: I2bcc4bb3325c2e69e27d0deef188272c943ab6ce