[legacy sf flag] - Remove legacyFrontEndEnabled

legcayFrontEndEnabled is always false and logic guarded
behind the flag can be deleted. Modifies test to
specially enable mLayerLifecycleEnabled since it is
false by default and needs to be enabled to use the new
front end path.

Bug: b/330785038
Test: presubmit
Test: atest ColorMatrixTest
Change-Id: I322f86674baaac185a62bbfe3ee27160688392f4