vt: bracketed paste support

This is comprised of 3 aspects:

- Take note of when applications advertise bracketed paste support via
  "\e[?2004h" and "\e[?2004l".

- Insert bracketed paste markers ("\e[200~" and "\e[201~") around pasted
  content in paste_selection() when bracketed paste is active.

- Add TIOCL_GETBRACKETEDPASTE to return bracketed paste status so user
  space daemons implementing cut-and-paste functionality (e.g. gpm,
  BRLTTY) may know when to insert bracketed paste markers.

Link: https://en.wikipedia.org/wiki/Bracketed-paste

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250520171851.1219676-2-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/uapi/linux/tiocl.h

@@ -36,5 +36,6 @@ struct tiocl_selection {
 #define TIOCL_BLANKSCREEN	14	/* keep screen blank even if a key is pressed */
 #define TIOCL_BLANKEDSCREEN	15	/* return which vt was blanked */
 #define TIOCL_GETKMSGREDIRECT	17	/* get the vt the kernel messages are restricted to */
+#define TIOCL_GETBRACKETEDPASTE	18	/* get whether paste may be bracketed */
 
 #endif /* _LINUX_TIOCL_H */