Move libmediahelper into a new folder.

This change mainly aims at refactoring libmediahelper. Libmediahelper
doesn't need to be stored in media folder. In that case, move
libmediahelper related file to a new folder. In the meantime, move
AudioParameter.h from libaudioclient to libmediahelper. There is no
need to keep AudioParameter.h in libaudioclient while AudioParameter.cpp
is in libmediahelper.

Test: make
Bug: 135621476
Change-Id: Icce6615b7e3a68be8b7492f2a91922ab04464ca2
Merged-In: Icce6615b7e3a68be8b7492f2a91922ab04464ca2