test_events: Promote check_events_dict to module level.
test_events: Promote check_events_dict to module level.

I want to avoid creating the same scheme checkers
for multiple tests, and it's easiest to create the
schema checkers at module scope (and we possibly
even move them to another file eventually).

This will allow us to more easily instrument our
code to find duplicate schemas.

punchagan/zulip,hackerkid/zulip,zulip/zulip,showell/zulip,punchagan/zulip,rht/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,synicalsyntax/zulip,rht/zulip,showell/zulip,brainwane/zulip,andersk/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,brainwane/zulip,hackerkid/zulip,brainwane/zulip,andersk/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,eeshangarg/zulip,brainwane/zulip,hackerkid/zulip,andersk/zulip,synicalsyntax/zulip,rht/zulip,showell/zulip,synicalsyntax/zulip,hackerkid/zulip,kou/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,punchagan/zulip,rht/zulip,zulip/zulip,brainwane/zulip,showell/zulip,zulip/zulip,eeshangarg/zulip,brainwane/zulip,rht/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,showell/zulip,hackerkid/zulip,synicalsyntax/zulip,zulip/zulip,synicalsyntax/zulip,showell/zulip,eeshangarg/zulip,kou/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,kou/zulip,punchagan/zulip,kou/zulip,synicalsyntax/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,synicalsyntax/zulip,zulip/zulip