e2e: fix the timeout code for expect_unordered

e2e: Add a 10s timeout for expect_stanza

Otherwise, if we expect a stanza and biboumi never sends it, we just hang
here.

Now, we display a nice error after 10 seconds, and move on to the next test,
as other failures (xpath doesn’t match) do

e2e: Implicitely include the handshake in all tests

Instead of having to write it manually everytime

Clean the __main__ file of the e2e tests

I forgot to remove some things when I moved them into functions.py

Split all the e2e tests in their own files

Some duplication is avoided, but most importantly: it’s much much cleaner,
easier to find, functions have been cleaned up (functools.partial usages are
now hidden), etc.

Remove a duplicate e2e test

Add tests for non anonymous rooms

See #3390

Expect a 210 code in the "change nick on join" e2e test

Update the e2e test to work with latest slixmpp

Update the tests to reflect the next->complete change

Add a test for outgoing /me messages that confirms issue #3382

XEP-0410: set not-in-the-room error condition to not-acceptable

XEP-0410 demands that. This changes the error condition for all
pings to the room, even those which aren’t self-pings, if the
sender is not joined.

The conditions of XEP-0410 were based on observing existing
implementations.

XEP-0410: implement server-side optimisation for self-pings

This prevents the ping from round-tripping through IRC and
possibly a random other client of the user. Please see XEP-0410
for the rationale.

Fixes #3385.

Do not send the IRC host directly as real JID of the user

Fixes #3381

Add a test demonstrating #3378

Flush stdout between each e2e test

Disable the throttle limit if negative

Also, invalid values result in -1 being set

Fix a few e2e tests that could fail due to race condition

The order of the messages received can be different, if the IRC server
decides so, or lags, or something.

Add two more sleeps, for the same reason

Disable the throttling for two tests that are very very long