Move allow rules of sdk_sandbox to apex policy

Third attempt to roll-forward the apex_sepolicy changes from
aosp/2179294 and aosp/2170746.

I was finally able to figure out the likely root cause of the test
breakages in internal b/243971667. The related CL aosp/2199179 is making
the apex_sepolicy files mandatory for all AOSP builds.

Without the apex_sepolicy files, mixed GSI builds in internal using AOSP
as base would not implement the sdk_sandbox rules, causing breakages for
the SdkSandbox components.

Bug: 243923977
Test: atest SeamendcHostTest
Change-Id: I27ee933da6648cca8ff1f37bde388f72b4fe6ad6
diff --git a/Android.mk b/Android.mk
index 21bc6a9..c3728fd 100644
--- a/Android.mk
+++ b/Android.mk
@@ -477,6 +477,7 @@
 LOCAL_REQUIRED_MODULES += precompiled_sepolicy.product_sepolicy_and_mapping.sha256
 endif
 
+LOCAL_REQUIRED_MODULES += precompiled_sepolicy.apex_sepolicy.sha256
 endif # ($(PRODUCT_PRECOMPILED_SEPOLICY),false)