idmap2: switch to improved Result class

Remove the old std::optional based Result class, replace uses with the
new std::variant based Result class.

Test: make idmap2_tests
Change-Id: I401cb36e5af06133a2872d835cf29bfb0b106597
diff --git a/cmds/idmap2/tests/FileUtilsTests.cpp b/cmds/idmap2/tests/FileUtilsTests.cpp
index 2e85eb6..34a0097 100644
--- a/cmds/idmap2/tests/FileUtilsTests.cpp
+++ b/cmds/idmap2/tests/FileUtilsTests.cpp
@@ -58,21 +58,15 @@
   });
   ASSERT_THAT(v, NotNull());
   ASSERT_EQ(v->size(), 10U);
-  ASSERT_EQ(
-      std::set<std::string>(v->begin(), v->end()),
-      std::set<std::string>(
-          {
-              root + "/target/target.apk",
-              root + "/target/target-no-overlayable.apk",
-              root + "/overlay/overlay.apk",
-              root + "/overlay/overlay-no-name.apk",
-              root + "/overlay/overlay-no-name-static.apk",
-              root + "/overlay/overlay-static-1.apk",
-              root + "/overlay/overlay-static-2.apk",
-              root + "/signature-overlay/signature-overlay.apk",
-              root + "/system-overlay/system-overlay.apk",
-              root + "/system-overlay-invalid/system-overlay-invalid.apk"
-          }));
+  ASSERT_EQ(std::set<std::string>(v->begin(), v->end()),
+            std::set<std::string>(
+                {root + "/target/target.apk", root + "/target/target-no-overlayable.apk",
+                 root + "/overlay/overlay.apk", root + "/overlay/overlay-no-name.apk",
+                 root + "/overlay/overlay-no-name-static.apk",
+                 root + "/overlay/overlay-static-1.apk", root + "/overlay/overlay-static-2.apk",
+                 root + "/signature-overlay/signature-overlay.apk",
+                 root + "/system-overlay/system-overlay.apk",
+                 root + "/system-overlay-invalid/system-overlay-invalid.apk"}));
 }
 
 TEST(FileUtilsTests, ReadFile) {