tdf#129522 ooxmlexport: allow char shadow_NONE override

tdf#129522 ooxmlexport: allow char shadow_NONE override

Normally we would NOT want to write out nil borders or shadows.
However, if these would be inherited, NILs needs to be written out.
This already worked for paragraphs, so it was just a matter
of identifying the character styles and testing against them.

I couldn't find anything that clearly stated that ChpIter
is the CharStyle properties, but it appears to act that
way, since the first check is for ISet (which seems to be
direct properties) and the second check is usually for
styles, and the Internet also suggests Fkp's are for styles.

This is the last patch in a series, and provides the
unit test for a previous import fix.

import depends on commit ccfccf4365362b5ba1d82b5816d5fc81a67de548
which depends on commit 4ca73073a0d7c62b12a7354f76f8f80adc5d98c1
and for export depends on commit
f84b33275f6cce21e93e5dd20f3de5df84df0276.

Change-Id: I5230adc52196b9b610d7863397bf33143682370c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/85870
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>