Inputflinger: hook up key event replacement processing

Add handling of "replacement" key events in InputReader and EventHub by
consulting device's character key map (if exists) for presence of
replacement key code for given get code and meta state combination,
before passing it to InputDispatcher.

This enables defining special keys, such as ESC, on keyboards lacking
enough physical keys, via combination of normal keys and modifiers, for
example AltR + 1 => ESC.

Bug: 24504154

Change-Id: I7e36104808bedcf724436c1fbb63d37c35cca8af