Factor out Rust client library for VirtualizationService.

This reduces code duplication, and will also be useful for Rust tests.

Test: ComposHostTestCases compos_key_tests
Change-Id: I13c41d3b2bbe506495b723e7739f3181cb033f0f
diff --git a/compos/composd/Android.bp b/compos/composd/Android.bp
index 55a3107..3a6119f 100644
--- a/compos/composd/Android.bp
+++ b/compos/composd/Android.bp
@@ -24,6 +24,7 @@
         "liblog_rust",
         "librustutils",
         "libshared_child",
+        "libvmclient",
     ],
     apex_available: [
         "com.android.compos",