vt: introduce gen_ucs_recompose.py to create ucs_recompose.c

vt: introduce gen_ucs_recompose.py to create ucs_recompose.c

The generated code includes a table that maps base character + combining
mark pairs to their precomposed equivalents using Python's unicodedata
module. It also provides the ucs_recompose() function to query that
table.

The default script behavior is to create a table with most commonly used
Latin, Greek, and Cyrillic recomposition pairs only. It is much smaller
than the table with all possible recomposition pairs (71 entries vs 1000
entries). But if one needs/wants the full table then simply running the
script with the --full argument will generate it.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://lore.kernel.org/r/20250410011839.64418-7-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>