Remove obsolete class loader context API and update unit tests.

The removed API has been unused since https://r.android.com/1533342
(except for unit tests).

Changes in the unit tests reflect the change of API in
https://r.android.com/1533342: early errors caused by unknown library
paths at CLC construction time have been replaced with late errors at
the time of CLC validation.

Bug: 132357300
Test: m nothing
Change-Id: I739c7c41b6f882b7e28cdd6acd05961d754d8687