misctrl: add a property

misctrl can set properties which can be injected into
bugreports.

Limit visibility of these properties so that no device
code can branch based off these properties.

Bug: 317262681
Test: bugreport
Change-Id: I74f6f240b08b2681540bca262dcc76bcdca9cdad
diff --git a/private/property_contexts b/private/property_contexts
index 568bdc1..fe12202 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -98,6 +98,7 @@
 ro.boot.serialno        u:object_r:serialno_prop:s0
 ro.bt.                  u:object_r:bluetooth_prop:s0
 ro.boot.bootreason      u:object_r:bootloader_boot_reason_prop:s0
+ro.misctrl.             u:object_r:misctrl_prop:s0
 persist.sys.boot.reason u:object_r:last_boot_reason_prop:s0
 sys.boot.reason         u:object_r:system_boot_reason_prop:s0
 sys.boot.reason.last    u:object_r:last_boot_reason_prop:s0