Reimplement functions deprecated in freerdp 3.11

FreeRDP 3.11 deprecated some keyboard related functions: https://github.com/FreeRDP/FreeRDP/commit/c29e93f4b29137885ac86a69e2ef15e3dd7ea087#diff-828a86140e4a8b99c4b323b6a98e85e4277e758b0e03ee43581409ee762c2336R268

freerdp_keyboard_init_ex can be removed completely, since it was only used by FreeRDP to try to determine a keyboard layout if none is provided, and krdc always provides one from connection preferences. Note: the keyboard layout specified in connection preferences is only useful in the login screen, since after login the remote user preferences layout will be used anyway.