Introduce vendor_microdroid_file for microdroid vendor image

In AVF, virtualizationmanager checks the selinux label of given disk
image for proving whether the given image is edited maliciously.
Existing one(vendor_configs_file, /vendor/etc/*) was too wide to use for this purpose.

Bug: 285854379
Test: m
Change-Id: I6c966c92b238a2262d2eb7f41041ed4c359e9e0a
diff --git a/private/shell.te b/private/shell.te
index aa6bef8..e410862 100644
--- a/private/shell.te
+++ b/private/shell.te
@@ -132,6 +132,9 @@
 allow shell self:perf_event { open read write kernel };
 neverallow shell self:perf_event ~{ open read write kernel };
 
+# Allow shell to read microdroid vendor image
+r_dir_file(shell, vendor_microdroid_file)
+
 # Allow shell to read /apex/apex-info-list.xml and the vendor apexes
 allow shell apex_info_file:file r_file_perms;
 allow shell vendor_apex_file:file r_file_perms;