SDK / exoplayer

When we currently call SessionToken.createSessionToken with a legacy
token, we call the package manager to get the process UID. This
requires visiblity to the target package, which may not be available
unless the target runs a service known to the controller app.

However, when connecting to a Media3, this UID doesn't have to be
known, so we can move the call closer to where it's needed to
avoid the unncessary visibility check.

In addition, a legacy session may reply with unknown result code
to the session token request, which we should handle as well.

One of the constructor can be removed since it was only used from
a test.

PiperOrigin-RevId: 489917706
(cherry picked from commit 2fd4aac3)