Relates to #5013.
Adds a debug status page to allow the user to select an alternative
platform so they can debug rules relating to those platforms which
are constrained by the `platform()` statement in the keyboard source.
Note that while touch platforms are listed here, there is not yet any
method of activating touch key events (e.g. `[T_foo]`). This
functionality is planned for a future update.
Refactors visual keyboard import from kmx to use Keyman Core, and at the
same time removes any UI interactions or direct Windows dependencies
from the process.
