Migrate VirtualMachine API to @SystemApi

Mark all the public members of the existing internal platform API as
@SystemApi (except for some @TestApi methods).

Update system-current.txt & test-current.txt to match.

Modify the demo app and the test APK and dependencies to build against
system / test SDK (respectively), instead of the implementation JAR /
platform APIs. (We still use platform APIs for the native payload code
though.)

Bug: 243512115
Test: atest MicrodroidTests MicrodroidHostTestCases
Test: Install & run demo app
CTS-Coverage-Bug: 244561836
Change-Id: Ibfffbb221f3ac37e03d5cfdbc9208428eeadbb9f
diff --git a/tests/testapk/Android.bp b/tests/testapk/Android.bp
index 707dca1..df7c6c0 100644
--- a/tests/testapk/Android.bp
+++ b/tests/testapk/Android.bp
@@ -19,15 +19,12 @@
         "truth-prebuilt",
         "compatibility-common-util-devicesidelib",
     ],
-    // We need to compile against the .impl library which includes the hidden
-    // APIs. Once the APIs are promoted to @SystemApi we can switch to
-    // framework-virtualization, which contains API stubs.
-    libs: ["framework-virtualization.impl"],
+    sdk_version: "test_current",
     jni_libs: [
         "MicrodroidTestNativeLib",
         "MicrodroidIdleNativeLib",
     ],
-    platform_apis: true,
+    jni_uses_platform_apis: true,
     use_embedded_native_libs: true,
     // We only support 64-bit ABI, but CTS demands all APKs to be multi-ABI.
     compile_multilib: "both",