Log split metrics through individual sessions

* Now we log the original source of the first selected app
as soon as the user selects it (previously we only did when user
selected second app)
* We log the item info for the second app to determine second
surface.
* Added new metrics to log after user has started a split session
and ended a split session
* We log different cancellation reasons (cancel button,
home gesture, general other app interruptions, etc).
* One KI/Bug: When the second app is selected via taskbar in
overview, the container will say hotseat because we are using
Launcher's logger and not Taskbar's. Taskbar's logger manually
overwrites the container in TaskbarActivityContext, we may be
able to make something hacky that can allow us to overwrite, but
that'll have to be a separate change

Bug: 322551862
Test: Logged metrics manually with event and itemInfo
Change-Id: I177623fd00ce62acf2d4ee983b58561d8c946d59