Add support for multiple GKI versions on VM

virt apex can now have multiple GKI versions for microdroid. Here are
behavior changes.

- OS name with "microdroid_gki-{ver}" is used to specify GKI.
- vm info shows available versions.
- gki option of vm tool gets a parameter, e.g. "--gki 6.1".

Some codes are refactored.

- Android.bp: defaults modules are added for deduplication.
- sign_virt_apex.py: gki_versions are added to remove hard-coded
  version (6.1).

Bug: 302465542
Test: vm info, vm run-microdroid --gki 6.1
Test: sign_virt_apex_test
Change-Id: I443a9e5a98d20d3c9337f2c13156590b4538c90b
diff --git a/apex/Android.bp b/apex/Android.bp
index f2a0d64..d3e736f 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -142,10 +142,10 @@
         },
         release_avf_enable_vendor_modules: {
             prebuilts: [
-                "microdroid_gki_initrd_debuggable",
-                "microdroid_gki_initrd_normal",
-                "microdroid_gki_kernel",
-                "microdroid_gki.json",
+                "microdroid_gki-6.1_initrd_debuggable",
+                "microdroid_gki-6.1_initrd_normal",
+                "microdroid_gki-6.1_kernel",
+                "microdroid_gki-6.1.json",
             ],
         },
     },