Inherit base system_ext.mk files for aosp targets

Make aosp targets inherit handheld_system_ext.mk and
telephony_system_ext.mk files.
Devices that have /system_ext or /system/system_ext must inherit any
of *_system_ext.mk files to install mandatory packages for system_ext
partition.

Also removed root/init.zygote64_32.rc from the whitelist because it
is already included in mainline_system.mk that does not required to
be whitelisted.

Bug: 144542478
Test: Build aosp targets
Change-Id: I9e4574f8dd54acfd8c2e59e49e0386b1678ab6af
1 file changed