Move APIs for querying platform mmap policy to AAudio.h

The two APIs for querying platform mmap policy is public NDK. Those
APIs can be used by apps. In that case, it makes more sense to have
those APIs in AAudio.h

Bug: 378909883
Test: atest AAudioTests
Flag: EXEMPT NDK
Change-Id: I59de609c62656027af632fce41ba246a3e249526