Add group_system_ext and passwd_system_ext

Add the remaining group and passwd files for partitions that have
reserved AIDs.

Test: mainline checks pass
Change-Id: Iae62c9465e0144b77b1d804c17fe6e724a744da2

target/product/base_vendor.mk

@@ -48,6 +48,7 @@ PRODUCT_PACKAGES += \
     fs_config_dirs_nonsystem \
     gralloc.default \
     group_odm \
+    group_system_ext \
     group_vendor \
     init_vendor \
     libashmemd_hidl_client \
@@ -64,6 +65,7 @@ PRODUCT_PACKAGES += \
     libril \
     libvisualizer \
     passwd_odm \
+    passwd_system_ext \
     passwd_vendor \
     selinux_policy_nonsystem \
     shell_and_utilities_vendor \