Simplify requestCreateSessionWithRouter2

Removes some unnecessary code and also fixes what seems to be buggy
behavior. For example, we are overwriting the initiator package name
if the user handle is not provided.

Bug: b/279555229
Flag: EXEMPT refactor
Test: presubmit
Change-Id: Ib8eb09d5c22ea251a3a3e043eec889df33f2f789