Split libaaudio.so to internal and NDK part

This change moves almost everything from libaadio.so to
separate libaaudio_internal.so library. This is done to
avoid exporting symbols which apps are not allowed to use
but have them available for platform libraries by exporting
them from libaaudio_internal.so

Bug: http://b/69603741
Test: make
Merged-In: If93118ed2c266faf2964abf21e17b0b13df493d2
Change-Id: If93118ed2c266faf2964abf21e17b0b13df493d2