trying to fix the problem with hanging UI tests

Hey community,

as promised I looked into the problem with hanging UI tests and noticed
that there was a bug in the handling of the shutdown if the LibreOffice
instance can not handle an UNO based shutdown request. The most common case
for this is actually hitting an assert in the UI tests while a modal dialog
is open.

I have proposed https://gerrit.libreoffice.org/c/core/+/95300 but that
attempt was rejected by Stephan and Noel. As I'm currently not involved
enough any more I'll leave the decision about the patch with the community.
I think without the patch one can just remove the whole UI test suite as
you can not safely use an assert if a dialog is still open (or could not be
closed). The patch makes sure that actually after each test case the
soffice process will be either correctly closed or receives a SIGTERM.

A simple test case is attached to the gerrit request that will result in a
soffice process not being closed properly without the patch. As a result,
later test runs will try to use the user profile of the still running
soffice instance and fail immediately until the soffice process is killed
manually.

My impression from this interaction is that some community members would
prefer to get rid of the UI tests completely instead of trying to fix the
current issue with the tests. I have decided not to invest any more of my
spare free time into this.

Cheers,
Markus