Audio HAL: Simplify types updates for 'common' and 'audio' packages

Instead of importing every single type individually ("using <type>"),
import entire namespaces of
::android::hardware::audio::CPP_VERSION and
::android::hardware::audio::common::CPP_VERSION
inside the "implementation" namespace in the default implementation.

This simplifies modifying types, as it is not needed anymore
to surround "using <type>" directives with #if MAJOR_VERSION ...

Note that the contents of the namespaces are imported inside
the "implementation" namespace, which reduces risks of name collision

Also, fixed the namespace for HidlUtils--it needs to be in
'implementation'.

Test: make
Change-Id: I8461d2ac3ad5d8ad4df4a15d99430ae0d7a5ccef