tests: Add more testing for patching bots.
tests: Add more testing for patching bots.

This commit adds some more tests related to patching
a bot's `default_sending_stream`.

Unfortunately, this didn't reach the code that I was
intending to add line coverage to, since checks happen
higher up in the stack, but the test code I added
is probably worthwhile.

rht/zulip,timabbott/zulip,jackrzhang/zulip,synicalsyntax/zulip,tommyip/zulip,timabbott/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip,brainwane/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,shubhamdhama/zulip,kou/zulip,rishig/zulip,punchagan/zulip,dhcrzf/zulip,andersk/zulip,timabbott/zulip,dhcrzf/zulip,hackerkid/zulip,shubhamdhama/zulip,zulip/zulip,jackrzhang/zulip,dhcrzf/zulip,andersk/zulip,dhcrzf/zulip,brainwane/zulip,timabbott/zulip,kou/zulip,jackrzhang/zulip,andersk/zulip,eeshangarg/zulip,tommyip/zulip,showell/zulip,brainwane/zulip,hackerkid/zulip,showell/zulip,shubhamdhama/zulip,kou/zulip,punchagan/zulip,rishig/zulip,showell/zulip,eeshangarg/zulip,showell/zulip,tommyip/zulip,timabbott/zulip,kou/zulip,showell/zulip,rishig/zulip,rishig/zulip,jackrzhang/zulip,rishig/zulip,brainwane/zulip,synicalsyntax/zulip,eeshangarg/zulip,jackrzhang/zulip,shubhamdhama/zulip,rishig/zulip,punchagan/zulip,hackerkid/zulip,dhcrzf/zulip,tommyip/zulip,synicalsyntax/zulip,zulip/zulip,eeshangarg/zulip,tommyip/zulip,andersk/zulip,rht/zulip,tommyip/zulip,showell/zulip,shubhamdhama/zulip,rht/zulip,zulip/zulip,rht/zulip,andersk/zulip,shubhamdhama/zulip,brainwane/zulip,dhcrzf/zulip,synicalsyntax/zulip,tommyip/zulip,synicalsyntax/zulip,rht/zulip,rht/zulip,andersk/zulip,hackerkid/zulip,synicalsyntax/zulip,dhcrzf/zulip,showell/zulip,eeshangarg/zulip,brainwane/zulip,brainwane/zulip,synicalsyntax/zulip,timabbott/zulip,punchagan/zulip,punchagan/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,jackrzhang/zulip,rishig/zulip,timabbott/zulip,punchagan/zulip,andersk/zulip,eeshangarg/zulip,punchagan/zulip,zulip/zulip,jackrzhang/zulip,zulip/zulip,shubhamdhama/zulip,zulip/zulip