Move hiddenapi config into frameworks/base/boot

As part of the work to modularize the hiddenapi this change moves the
hiddenapi configuration files into the frameworks/base/boot directory
which is where the platform_bootclasspath module that will end up
using it resides.

Bug: 179354495
Test: verified that the out/soong/hiddenapi/... files are unchanged
      by this change
Change-Id: Ic1c3ac9b717c34fa8ff36f349a75fb397101a077