Use /bootstrap-apex for bootstrap APEXes

This new directory is bind-mounted to /apex in the bootstrap mount
namespace so that apexd-bootstrap mounts bootstrap APEXes there via
/apex.

The directory is shared between two mount namespaces, hence visible
in the default mount namespace.

Bug: 290148078
Test: VendorApexHostTestCases
Change-Id: I841480e41be8def5a4c6a4aa874c4e21465a71d3
diff --git a/init/selinux.cpp b/init/selinux.cpp
index f34474f..ebdcaa6 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -757,7 +757,7 @@
     selinux_android_restorecon("/dev/device-mapper", 0);
 
     selinux_android_restorecon("/apex", 0);
-
+    selinux_android_restorecon("/bootstrap-apex", 0);
     selinux_android_restorecon("/linkerconfig", 0);
 
     // adb remount, snapshot-based updates, and DSUs all create files during