Add option to use GKI kernel for microdroid

With either payload config's osName field or config file's os field, a
GKI kernel can be used to run microdroid instead of microdroid kernel.
This also adds a new option --gki to the VM tool.

Bug: 305118971
Test: run VM with --gki
Change-Id: I87eb445c84bd208df549712aea7f55ab148c7f8a
diff --git a/apex/Android.bp b/apex/Android.bp
index 96540aa..e04dbd2 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -146,6 +146,7 @@
                 "microdroid_gki_initrd_debuggable",
                 "microdroid_gki_initrd_normal",
                 "microdroid_gki_kernel",
+                "microdroid_gki.json",
             ],
         },
     },