Remove use of legacy layers from composition test

Legacy layers are no longer used in production, this
changes the unit tests to use requestedlayerstate
directly.

This cl also removes two tests which exercised the layer hierarchy
which is now covered by layerhierarchy tests.

Flag: EXEMPT removing flagged code
Test: presubmit
Bug: 330785038

Change-Id: Icd043916791fec4c89ff267e1e43ab45e347a0ba