* 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.

* 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.

* Add option 'Space bar slider sensitivity'

* Fix slider moving the cursor twice at the beginning

The slider was generating two events when first activated.
Since 2bed42857.

* Make slider less sensitive for the first step

This moves the second slider step approximately 40% further and takes the
new sensitivity option into account.
Allows moving the cursor by one spot more easily.

This can be used on phones that have several screens.

* Add AndroidX WindowManager

unfortunately, this seems to be the only way to get fold state, native Android APIs are internal. To add this, we need to update some dependencies, raise java version and raise compile SDK.

* adds separate layouts and separate layout settings for folded and unfolded state of the device.

The affected settings are:
+ the margin bottom settings
+ the horizontal margin settings
+ the keyboard height settings

* Update shell.nix

The number row option is changed into a ListPreference and controls whether the number row contains symbols or not.

Co-authored-by: Joey Schaff <j@jaoh.xyz>