Refactor the LVGL terminal into a shared core (lvglterm.c) plus two
selectable input variants: the existing on-screen touch keyboard
(lvglterm_touch.c) and a new physical keyboard variant (lvglterm_kbd.c) that
reads key events from a /dev/kbdN device and streams them to the shell.
The input source is chosen with a Kconfig choice (touch by default, keeping
the previous behaviour). The keyboard variant reads its device from
CONFIG_EXAMPLES_LVGLTERM_KBD_DEV (default /dev/kbd0), overridable by the first
command-line argument, and scrolls the output with the Fn cursor keys. A font
choice (UNSCII 8 or 16) is added for low-resolution displays.
Signed-off-by: Jorge Guzman <jorge.gzm@gmail.com>
