Add policy for 'blank_screen'.

This util allows init to turn off the screen
without any binder dependencies.

Bug: 70846424
Test: manual + init use
Change-Id: I4f41a966d6398e959ea6baf36c2cfe6fcebc00de

private/blank_screen.te

+type blank_screen, domain, coredomain;
+type blank_screen_exec, exec_type, file_type;
+
+init_daemon_domain(blank_screen)
+
+hal_client_domain(blank_screen, hal_light)

private/compat/26.0/26.0.ignore.cil

@@ -5,6 +5,9 @@
 (typeattributeset new_objects
   ( adbd_exec
     bootloader_boot_reason_prop
+    blank_screen
+    blank_screen_exec
+    blank_screen_tmpfs
     bpfloader
     bpfloader_exec
     broadcastradio_service

private/file_contexts

@@ -179,6 +179,7 @@
 #
 /system(/.*)?		u:object_r:system_file:s0
 /system/bin/atrace	u:object_r:atrace_exec:s0
+/system/bin/blank_screen	u:object_r:blank_screen_exec:s0
 /system/bin/e2fsdroid		u:object_r:e2fs_exec:s0
 /system/bin/mke2fs		u:object_r:e2fs_exec:s0
 /system/bin/e2fsck	--	u:object_r:fsck_exec:s0