AidlConversion: Implement conversion between types from CPP and NDK

Implement universal conversion functions between types
from CPP and NDK backends generated from the same AIDL
definition. The conversion is implemented via marshalling
and unmarshalling. More performant conversions need to
be implemented manually.

Move enum converters from DeviceHalAidl to the new module.

Bug: 205884982
Test: atest audio_aidl_ndk_cpp_conversion_tests
Change-Id: I9c820d22c673381f2a2fa8c13bc938535fbe4467