Some general Python test improvements (#2316)

This PR originally contained a fix for sqlx which turned out not not to be necessary. But on the way, I made some general improvements:

- Under some circumstances, a "normal" test failure led to a timeout, without printing a decent error message. See e.g. https://app.circleci.com/pipelines/github/deltachat/deltachat-core-rust/8069/workflows/ba2a9949-b4ad-4ceb-a930-073bba05e2db/jobs/30965.
  (The problem was: if there is an exception in dc_account_extra_configure(), when trying to handle the exception the line account.log("===================", e, "===================") was called, which can't work as log() only expects one parameter)
- When a test fails: Call `dump_account_info()` even if there is no direct_imap
- In test_import_export_online_all(), add another 100KB file to the backup. This adds resilience against future size changes of the sql db file: The test tests the smoothness of the progress bar. And if there are there are not enough about-equally-sized files, the progress bar can't be smooth.

python/src/deltachat/testplugin.py

@@ -414,13 +414,13 @@ def acfactory(pytestconfig, tmpdir, request, session_liveconfig, data):
 
         def dump_imap_summary(self, logfile):
             for ac in self._accounts:
+                ac.dump_account_info(logfile=logfile)
                 imap = getattr(ac, "direct_imap", None)
                 if imap is not None:
                     try:
                         imap.idle_done()
                     except Exception:
                         pass
-                    imap.dump_account_info(logfile=logfile)
                     imap.dump_imap_structures(tmpdir, logfile=logfile)
 
         def get_accepted_chat(self, ac1, ac2):