Remove default_shared_libs

system_shared_libs has been modified to have the same behavior as
the newly added default_shared_libs, remove default_shared_libs in
favor of system_shared_libs.

This reverts Ia2349d84c70e503916f90a5d2702e135248f73df and renames
the default_shared_libs property in cc_object (which never had
system_shared_libs) to system_shared_libs.

Bug: 193559105
Test: m checkbuild
Change-Id: I46672e3a096b6ea94ff4c10e1c31e8fd010a163c