Keystore 2.0: Move test utils to separate library.

Move TempDir test utils to separate library for easier reuse.

Test: keystore2_test
Change-Id: If1edfde39b66efa43f8a5ed32a500fad57291512
diff --git a/keystore2/Android.bp b/keystore2/Android.bp
index 2ed2a60..70363ef 100644
--- a/keystore2/Android.bp
+++ b/keystore2/Android.bp
@@ -40,6 +40,16 @@
     ],
 }
 
+rust_library {
+    name: "libkeystore2_test_utils",
+    crate_name: "keystore2_test_utils",
+    srcs: ["test_utils/lib.rs"],
+    rustlibs: [
+        "liblog_rust",
+        "librand",
+    ]
+}
+
 rust_test {
     name: "keystore2_test",
     crate_name: "keystore2",
@@ -60,6 +70,7 @@
         "libkeystore2_crypto_rust",
         "libkeystore2_km_compat",
         "libkeystore2_selinux",
+        "libkeystore2_test_utils",
         "liblazy_static",
         "liblibc",
         "liblibsqlite3_sys",