Merge changes Iae1cbfcc,I4466838c,I19c75e50,I2f49fab1 into main

* changes:
  libprocessgroup: Remove __BEGIN_DECLS and __END_DECLS
  libprocessgroup: Convert CGROUPV2_HIERARCHY_NAME to std::string
  libprocessgroup: Remove CGROUPV2_CONTROLLER_NAME
  libprocessgroup: Remove CGROUPS_RC_PATH