This PR updates the ID used by logical keyboard keys.

The logical key ID is still composed of 2 parts: 32 bits of value, and 8 bits of plane. But the assignment of planes has been drastically changed. HID plane is removed, and unprintable plane and Flutter plane are added. This is to reflect the new generation method for logical key IDs. Now keys that are defined by Flutter but not by dom_key_data are placed into the Flutter plane, including numpad keys, sided modifier keys, and gamepad keys. The values for platform planes have also been adjusted.

The generation script and README have been updated accordingly as well.

A new file, test_utils/key_codes.h is now generated to assist engine unit testing.

All lists generated by the script are now sorted by the key.

This adds iOS key map generation that uses std::maps. It uses std::maps because on iOS if we use NSDictionaries, then when XCode loads the dylib, the initialization of those status NSDictionaries hasn't yet occurred, and it crashes the app. std::maps have a well-defined static behavior, and are correctly initialized.

I also made the naming of variables, fields, etc. consistent for macOS. We variously had macosFoo, macOSFoo, and macOsFoo. I eliminated macOsFoo and macosFoo, since the rest of the repo uses macOSFoo for lowerCamelCase names (with only a few exceptions). I used iOSFoo for iOS.

Removes webValues from logical_key_data.json. Web's logical mapping should map webNames to logical key values, i.e. entry.value.

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

* Added RawKeyEvent support for iOS

* Removed unused remnant

* added some missing keys

* Removed trailing whitespaces

* commit for build

* Added mapping names

* Made iOS keycodes generatable and collectable

* Fixed naming and formatting issues

* fixed raw_keyboard_test

* Split gen_keycode to make maintenance easier.