Add last finalized version to metadata file.

This CL builds the .latest.version target which contains the last
finalized version. This version is read and populated inside the
metadata file.
The CL also verifies whether all the java sdk libraries under a module,
which has been finalized atleast once, have the same extension version.

Bug: 242316893
Test: atest --host mainline_modules_sdks_test --no-bazel-mode
Change-Id: I94acf448b25d76c45a4bfd3d54fc276e2f01c7cc

build/mainline_modules_sdks_test.py

@@ -130,7 +130,11 @@ class FakeSnapshotBuilder(mm.SnapshotBuilder):
 
         for target_path in target_paths:
             os.makedirs(os.path.split(target_path)[0])
-            self.write_data_to_file(target_path, "")
+            if ".latest.extension_version" in target_path:
+                self.write_data_to_file(
+                    target_path, str(self.get_module_extension_version()))
+            else:
+               self.write_data_to_file(target_path, "")
 
         return target_dict
 
@@ -343,6 +347,11 @@ class TestProduceDist(unittest.TestCase):
             5,
             msg="The module extension version does not match the expected value."
         )
+        self.assertEqual(
+            json_data["last_finalized_version"],
+            5,
+            msg="The last finalized version does not match the expected value."
+        )
 
     def create_build_number_file(self):
         soong_dir = os.path.join(self.tmp_out_dir, "soong")