libcpp: Update to Unicode 15

The following pseudo-patch regenerates the libcpp tables with Unicode 15.0.0
which added 4489 new characters.

As mentioned previously, this isn't just a matter of running the
two libcpp/make*.cc programs on the new Unicode files, but one needs
to manually update a table inside of makeuname2c.cc according to
a table in Unicode text (which is partially reflected in the text
files, but e.g. in Unicode 14.0.0 not 100% accurately, in 15.0.0
actually accurately).
I've also added some randomly chosen subset of those 4489 new
characters to a testcase.

2022-11-04  Jakub Jelinek  <jakub@redhat.com>

gcc/testsuite/
	* c-c++-common/cpp/named-universal-char-escape-1.c: Add tests for some
	characters newly added in Unicode 15.0.0.
libcpp/
	* makeuname2c.cc (struct generated): Update from Unicode 15.0.0
	table 4-8.
	* ucnid.h: Regenerated for Unicode 15.0.0.
	* uname2c.h: Likewise.