vectorcraft_testkit::temp_dir returns a bare path, so every engine test
that wrote into one left the folder in the system temporary folder.
- testkit: TempDir, a test's own folder made through temp_dir (same
private creation and ownership checks) under a tag no other TempDir in
the process uses, removed with its contents when dropped, also when
the test panics.
- Engine unit and integration tests hold a TempDir for the whole test
instead of calling temp_dir: graph, fileio, compare, journal, library,
shortcut set, spelling, store, web export, cancel, containers, build,
color settings, command sweep, font folder, removed font, model-based
and the font search fuzz.
- The DCS and swatch library tests' own helpers and the PDF editing
tests' shared vc-pdfedit-<pid> folder use a TempDir per test too.
- The font and link file search, store, color settings and font folder
helpers no longer delete the private folder temp_dir checked and make
it again with default permissions.
dotCooCoo