Re: split func.sgml to separated individual sgml files

hi.

after run the v2 python script and ``git apply
v2-0001-update-filelist.sgml-allfiles.sgml.no-cfbot``
git status -u
shows:

Changes not staged for commit:
(use "git add/rm <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: doc/src/sgml/filelist.sgml
deleted: doc/src/sgml/func.sgml

That means to verify the changes, we only need to verify html files
related to "functions".

I use GNU diff to compare the HTML output of doc/src/sgml/func.sgml generated
from the master branch against the HTML file produced by the patch.
For example, $DOC9 is the PATCH (split func.sgml) html file directory, $DOC5 is
the master branch html file directory. and no message produced while running
diff, which means the patch (with the script) produced output is the
same as the master branch.

diff $DOC5/functions.html $DOC9/functions.html
diff $DOC5/functions-logical.html $DOC9/functions-logical.html
diff $DOC5/functions-comparison.html $DOC9/functions-comparison.html
diff $DOC5/functions-math.html $DOC9/functions-math.html
diff $DOC5/functions-string.html $DOC9/functions-string.html
diff $DOC5/functions-binarystring.html $DOC9/functions-binarystring.html
diff $DOC5/functions-matching.html $DOC9/functions-matching.html
diff $DOC5/functions-formatting.html $DOC9/functions-formatting.html
diff $DOC5/functions-datetime.html $DOC9/functions-datetime.html
diff $DOC5/functions-enum.html $DOC9/functions-enum.html
diff $DOC5/functions-geometry.html $DOC9/functions-geometry.html
diff $DOC5/functions-net.html $DOC9/functions-net.html
diff $DOC5/functions-textsearch.html $DOC9/functions-textsearch.html
diff $DOC5/functions-uuid.html $DOC9/functions-uuid.html
diff $DOC5/functions-xml.html $DOC9/functions-xml.html
diff $DOC5/functions-json.html $DOC9/functions-json.html
diff $DOC5/functions-sequence.html $DOC9/functions-sequence.html
diff $DOC5/functions-conditional.html $DOC9/functions-conditional.html
diff $DOC5/functions-array.html $DOC9/functions-array.html
diff $DOC5/functions-range.html $DOC9/functions-range.html
diff $DOC5/functions-aggregate.html $DOC9/functions-aggregate.html
diff $DOC5/functions-window.html $DOC9/functions-window.html
diff $DOC5/functions-merge-support.html $DOC9/functions-merge-support.html
diff $DOC5/functions-subquery.html $DOC9/functions-subquery.html
diff $DOC5/functions-comparisons.html $DOC9/functions-comparisons.html
diff $DOC5/functions-srf.html $DOC9/functions-srf.html
diff $DOC5/functions-info.html $DOC9/functions-info.html
diff $DOC5/functions-admin.html $DOC9/functions-admin.html
diff $DOC5/functions-trigger.html $DOC9/functions-trigger.html
diff $DOC5/functions-event-triggers.html $DOC9/functions-event-triggers.html
diff $DOC5/functions-statistics.html $DOC9/functions-statistics.html