vt: create ucs_recompose.c using gen_ucs_recompose.py

vt: create ucs_recompose.c using gen_ucs_recompose.py

This provides ucs_recompose() to recompose two Unicode characters into
a single character if possible. This is needed for the VT to properly
display decomposed UTF8 sequences.

Note: scripts/checkpatch.pl complains about "... exceeds 100 columns".
      Please ignore.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://lore.kernel.org/r/20250410011839.64418-8-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>