Add test for 'throttle-ui-updates' config

Background

With !1745 (merged) landing, it would probably be beneficial to add tests to check the non restricted behaviour & also ensuring the default tick driven UI is functional. This could potentially harness something along the lines of the pexpect fixtures we already have, parsing the inflight session pager although input interactivity isn't actually needed. Something as simple as checking the status area would probably suffice.

---