Hardware keyboard: codegen (#73440)

Rewrites tools/gen_keycodes, the script that generates key mappings across the framework and the engine.

dev/tools/gen_keycodes/data/android_keyboard_map_java.tmpl

@@ -0,0 +1,34 @@
+package io.flutter.embedding.android;
+
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
+// This file is generated by flutter/flutter@dev/tools/gen_keycodes/bin/gen_keycodes.dart and
+// should not be edited directly.
+//
+// Edit the template dev/tools/gen_keycodes/data/android_keyboard_map_java.tmpl instead.
+// See dev/tools/gen_keycodes/README.md for more information.
+
+import java.util.HashMap;
+
+public class KeyboardMap {
+  public static final HashMap<Long, Long> scanCodeToPhysical =
+      new HashMap<Long, Long>() {
+        private static final long serialVersionUID = 1L;
+
+        {
+@@@ANDROID_SCAN_CODE_MAP@@@
+        }
+      };
+
+  public static final HashMap<Long, Long> keyCodeToLogical =
+      new HashMap<Long, Long>() {
+        private static final long serialVersionUID = 1L;
+
+        {
+@@@ANDROID_KEY_CODE_MAP@@@
+        }
+      };
+}