libprocessgroup: Add libcgrouprc

This module is an LL-NDK library that can be loaded by
modules that link to libprocessgroup (which is in VNDK).
This module defines APIs that reads cgroups.rc file
programatically. Internally, it uses libcgrouprc_format to
do so.

Test: builds
Bug: 123664216

Change-Id: I9c13c0528461758154e23cbab3a94ade7fb351ee
Merged-In: I9c13c0528461758154e23cbab3a94ade7fb351ee