Verify that the VM-generated BCC is valid

Commit 5430ecaaa2deb9d1e0077c2e2e0a72e89540da76 causes the CompOS VM
to write its BCC to file.

Augment our tests to pull that file and run it through the
bcc_validator to make sure the chain is valid (each entry is
well-formed, the signatures all check out, etc). Also add the BCC file
to the test artifacts.

While I'm here, do some minor tidying up.

Bug: 225177477
Test: atest android.compos.test.ComposTestCase#testOdrefreshSpeed
Change-Id: I544d9086fb875eb8987868555bcb99de42ac7f6b
diff --git a/compos/tests/Android.bp b/compos/tests/Android.bp
index c178ddd..b77a7e4 100644
--- a/compos/tests/Android.bp
+++ b/compos/tests/Android.bp
@@ -10,6 +10,7 @@
         "compatibility-tradefed",
         "compatibility-host-util",
     ],
+    data_native_bins: ["bcc_validator"],
     static_libs: [
         "VirtualizationTestHelper",
     ],