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.

tests/end_to_end/scenarios/self_disco_info.py

@@ -0,0 +1,12 @@
+from scenarios import *
+
+scenario = (
+    sequences.handshake(),
+    send_stanza("<iq type='get' id='get1' from='{jid_one}/{resource_one}' to='{biboumi_host}'><query xmlns='http://jabber.org/protocol/disco#info'/></iq>"),
+    expect_stanza("/iq[@type='result']/disco_info:query/disco_info:identity[@category='conference'][@type='irc'][@name='Biboumi XMPP-IRC gateway']",
+                  "/iq/disco_info:query/disco_info:feature[@var='jabber:iq:version']",
+                  "/iq/disco_info:query/disco_info:feature[@var='http://jabber.org/protocol/commands']",
+                  "/iq/disco_info:query/disco_info:feature[@var='urn:xmpp:ping']",
+                  "/iq/disco_info:query/disco_info:feature[@var='urn:xmpp:mam:2']",
+                  "/iq/disco_info:query/disco_info:feature[@var='jabber:iq:version']"),
+)