audio: Put audio/aidl/common/include/Utils.h into 'aidl' NS

These utilities are for types generated from AIDL. Since
the types end up in the 'aidl' namespace (NDK backend), it makes
sense to keep the utilities in the same namespace.

While changing the namespace, I've found numerous useless
includes of 'Utils.h' and removing them, also reorganizing
lists of includes along the way to match the style guide.

Bug: 205884982
Test: m
Test: atest --test-mapping hardware/interfaces/audio/aidl/TEST_MAPPING
Change-Id: Ib23b47092364046f632f9503b92b9baff5b902f5