This adds dictionary-based spell checking to the keyboard. The keyboard looks at the word being typed and matches it against a dictionary to either complete the rest of the word or find alternative spellings.

The core of this feature is implemented in cdict, which is included as a
submodule in vendor/cidct.

Cdict is developped at https://github.com/Julow/cdict
The dictionaries are hosted at https://github.com/Julow/Unexpected-Keyboard-dictionaries/
The wordlists used to build the dictionaries are the same ones used by
HeliBoard from https://codeberg.org/Helium314/aosp-dictionaries

- Add an activity accessible from the launcher app that lists available
  dictionaries with a download button.
  The DictionaryListView view shows the list of available dictionaries and
  handles downloading and installing them.

- The Dictionaries class manages installed dictionaries. Dictionaries are
  installed as individual files into the app's private directory.

- Available dictionaries are listed in dictionaries.xml, which is generated
  when building Unexpected-Keyboard-dictionaries.
  method.xml mentions the dictionary name for each locales.

* Refactor: Split DeviceLocales out of Keyboard2

This moves the code from Keyboard2 that handles the active IME subtypes
and the current one.

The goal is to access this information from the dictionary activity
while simplifying the code of Keyboard2.

* Refresh the candidates view when subtype changes

This fixes the status message being inconsistently shown.

* Refactor: Load DeviceLocales less often

Previously, [DeviceLocales.load()] was called everytime the keyboard was
shown on the screen. This operation is moderately costly and only need
to be done when the IME subtype changes.

* EditorConfig: Fix crash on Android 9