* gen_method_xml.py: Warn for unused dictionaries

Helps catch missing locales.

* Add languages for which a dictionary is available

Make dictionaries are available to more languages. Extra keys are added
for as many languages as possible but no layout is added.

Some languages are still not added, mainly because they use a script
that the keyboard doesn't support yet:

    pa, gu, or, te, mai, sat, km, iw, zgh, sd, ml, sa

The "en" locale, which was meant to be the default for English locales
that are not in the list, was used instead of exact locales like "en_US".

The "en" locale was also used as the default locale for languages that
are not in the list at all. The "en_GB" locale is used for this instead.

* Fix the spacebar in Hangul combining

The encoding for the spacebar changed and the Hangul combining code was
not updated.

* Change the default layout for Korean

Change default unknown locale dictionary from en_US to en_GB

* Refactor: Implement the space key as an editing action

The space key is no longer a CHAR key but now an EDITING key. This
allows changing the behavior of the space bar while allowing custom
layout users to define a key outputing a space as before.

KeyModifier and ComposeKey are updated to treat the space key as before.

* Enter the best suggestion when the space bar is pressed

* Refactor: Implement backspace as an editing action

* Undo suggestion when delete is pressed

The delete key (backspace internally) undoes the suggestion if the last
action done was entering the suggestion with either the space bar or the
candidates view.

* Add an option to enable space bar autocomplete

This option is off by default. Undoing a completion with backspace works
in any case.

* Refactor: Track selection emptyness in CurrentlyTypedWord

This removes an expensive RPC call.

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: Create subpackage 'suggestions'

* Candidates view: Status message when no dictionary installed

Show a message on the candidates view instead of leaving it empty. A
button points to the dictionary installation activity.

* Add an option to disable the suggestions

* Refactor: Remove Config.should_show_candidates_view

This was moved to EditorConfig.

* Don't disable text suggestions in some text boxes

* Suggestion text size matching settings

The candidates view height is based on the height of keyboard rows and
the suggestion text size is based on the size of labels on the keys.

This is influenced by symbol size and keyboard height options.

The "Switch to the last used keyboard" is renamed to "Switching between
input methods" and allows to select "Switch to last used", which was the
default in older releases.