file plug-in testing.
The name and location of the xml results will be the same as for the
log file, but with the extension replaced by .xml.
Just some basic support is added which adds failed testcases when
a plug-in has a failure result, which should be the most common
case of failures.
Not all cases where we make errors in our test setup will generate
failed testcases yet, although they should show up in the number of
failures.
Disabled tests won't show up as skipped tests.
We also don't track time.
for gimp-tests.log
On Linux we may not have permission to create a log at our default
location, so we need to check for that.
First we should not init the log when our plug-in is asked for info.
Only create it when we actually run the import or export tests.
Second, try to catch the permission error and write a message either
in GIMP or in the terminal for non-interactive.
Copied over from the original separate work in:
https://gitlab.gnome.org/Wormnest/gimp-file-plugin-tests
After that further improved and changed and added more file format
tests.
Added meson.build files to integrate it in our build, but we do not
install it for releases.
