Move loopdevice module to dm_rust lib

This is a generic module, not specific to apkdmverity. Will be reused
for unit-testing other dm- devices. Also, setup the test infra for
dm_rust module...

Bug: 250880499
Test: atest libdm_rust.test
Test: atest apkdmverity.test
Change-Id: I32971938908ea8c0213583885403910baac8be10
diff --git a/libs/devicemapper/Android.bp b/libs/devicemapper/Android.bp
index 61ffa22..088b320 100644
--- a/libs/devicemapper/Android.bp
+++ b/libs/devicemapper/Android.bp
@@ -27,3 +27,14 @@
     name: "libdm_rust",
     defaults: ["libdm_rust.defaults"],
 }
+
+rust_test {
+    name: "libdm_rust.test",
+    defaults: ["libdm_rust.defaults"],
+    test_suites: ["general-tests"],
+    rustlibs: [
+        "libscopeguard",
+        "libtempfile",
+    ],
+    data: ["tests/data/*"],
+}