Dump orphaned sessions is separate block

A child wihout its parent can never be installed. As such, it can't be
"Active install session".

Presence of orphaned sessions indicate leak in cleanup for multi-package
sessions. Creating a separate dumping block for orphaned sessions so
that we can catch leaks more easily.

Bug: 162518337
Test: use `adb install-multi-package --staged` to create multi-package
      session and then abandon the parent session to create orphaned
      child sessions. Made sure dumpsys isn't printing them anymore.
Change-Id: I36d7e7a88409d3d1582cb0554da9ed91e94a508d