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/raw_names_command.py

@@ -0,0 +1,13 @@
+from functions import send_stanza, expect_stanza
+
+import scenarios.simple_channel_join
+
+join_channel = scenarios.simple_channel_join.scenario
+
+scenario = (
+    join_channel,
+
+    send_stanza("<message type='chat' from='{jid_one}/{resource_one}' to='{irc_server_one}'><body>NAMES</body></message>"),
+    expect_stanza("/message/body[text()='irc.localhost: = #foo @{nick_one} ']"),
+    expect_stanza("/message/body[text()='irc.localhost: * End of /NAMES list. ']"),
+)