Restore applypatch/updater/edify for non-A/B OTA support

Google deleted this source from bootable/recovery outright (commit c7ebad5f,
"rm -rf non-AB code", 2024-04-05) — confirmed present at android-14, absent
at android-16.0.0_r4. The runtime side (install.cpp's SetUpNonAbUpdateCommands)
and build-side packaging (ota_from_target_files.py's GenerateNonAbOtaPackage)
both survived; only the source that builds the update-binary executable
itself was removed. Sourced from TeamWin's android_bootable_recovery
(android-14.1), the only living copy found, with install/ZipUtil.cpp,
get_args.cpp, and set_metadata.cpp intentionally left out (only wired into
TeamWin's modified install.cpp, which PawletOS isn't adopting — twrpinstall
carries its own independent copies).

Kept as its own repo, not folded into a recovery fork, so it's buildable
independent of whichever recovery UI ends up in use.

applypatch/applypatch_main.cpp

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "applypatch_modes.h"
+
+#include <android-base/logging.h>
+
+// See the comments for applypatch() function.
+int main(int argc, char** argv) {
+  android::base::InitLogging(argv);
+  return applypatch_modes(argc, argv);
+}