For some reason, we have never exported the default column width
to XLSX, although we have such export for XLS. This led to bugs
like tdf#100946. Workarounds applied to those bugs have made LO
to export columns which shouldn't have been exported, abusing
"customWidth" attribute in XclExpColinfo::XclExpColinfo depending
on if the column has size different from an app-global default;
after that, sheet-local default was determined, and then columns
which have mbCustomWidth set (i.e., different from app default),
as well as those different from sheet-local default, were stored.
Effectively, the hack had disabled the removal of defaults from
maColInfos in XclExpColinfoBuffer::Finalize. We even had unit
tests explicitly testing that we export those columns that Excel
skips. The effect of that is not only unnecessary data in the file;
the data was actually wrong (customWidth actually means that the
width was edited manually by user, even if equal to the default,
thus changing Excel handling of the column); and also Calc
initializes all columns to the right of last used column for such
a file. Only in case when app-global default happened to match
sheet-local one, columns would have properties allowing them to
be removed from maColInfos in the end of XclExpColinfoBuffer::Finalize,
which still resulted in problems similar to the workarounded one.

This patch implements proper export of the default column width
to XLSX, thus partially reverting changes made for tdf#100946 in
commit 40d892a2. Actually, our
export to XLSX does not depend on the 5-pixel correction (see
ECMA-376-1:2016 18.3.1.81), since the exported default depends
only on most-used column width. XclExpDefcolwidth implementation
was edited to only take the correction into account when exporting
to XLS (to keep status quo; it's clear that XLS widths export
and import implementation is incorrect: some empirical formula
is used in XclTools::GetXclDefColWidthCorrection, that was
introduced in commit 555d7029 for
i#3006, that doesn't match any documentation, and changes widths
of columns in exported XLS - something to be fixed independently).

Change-Id: I227aca17e56247cbb839444717066a898987c4f1
Reviewed-on: https://gerrit.libreoffice.org/71132Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Mike Kaganski <mike.kaganski@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/71222