Revert^2 audiopolicy: capengine: allow to disable AIDL Cap engine config

This CL allows to disable AIDL Cap engine configuration.
When disabled, CapEngine relies on legacy vendor XML file.

Bug: 379596346
Test: atest audiorouting_tests
atest audiosystem_tests
atest audiopolicy_tests
(with lunch target aosp_cf_x86_64_only_phone and
 aosp_cf_x86_64_auto migrated on cap engine)

Change-Id: I358324607f1cb3de1630f133eab22b28380ecba2
Signed-off-by: François Gaffie <francois.gaffie@ampere.cars>