ui: Remove ui_inchar/ui_char_avail

Also:

- Remove NO_CONSOLE_INPUT/NO_CONSULE preprocessor conditionals
- Remove ctrl_c_interrupts variable, check for mapped_ctrl_c directly in
  process_interrupts()
- Move ui_inchar profiling to input_poll which is where Nvim blocks for input.

src/nvim/message.c

@@ -2702,11 +2702,9 @@ do_dialog (
   int c;
   int i;
 
-#ifndef NO_CONSOLE
   /* Don't output anything in silent mode ("ex -s") */
   if (silent_mode)
     return dfltbutton;       /* return default option */
-#endif
 
 
   oldState = State;