Add boot_status_prop for boot completed props

Assigning a new context boot_status_prop for following two properties:
- sys.boot_completed
- dev.bootcomplete

Bug: 154885206
Test: boot cf_x86 and crosshatch, see no denials
Change-Id: Ieadabf90a9a1b54b52a1283bd648c11c95d558dd
Merged-In: Ieadabf90a9a1b54b52a1283bd648c11c95d558dd
(cherry picked from commit 2973c9605555c119243ef85119576b2d01a12060)
diff --git a/private/compat/27.0/27.0.ignore.cil b/private/compat/27.0/27.0.ignore.cil
index e41ee74..3fdb0b4 100644
--- a/private/compat/27.0/27.0.ignore.cil
+++ b/private/compat/27.0/27.0.ignore.cil
@@ -23,6 +23,7 @@
     blank_screen
     blank_screen_exec
     blank_screen_tmpfs
+    boot_status_prop
     bootloader_boot_reason_prop
     bluetooth_a2dp_offload_prop
     bpfloader