i15-1: Do not allow resuming the queue when it's empty

Following https://github.com/DiamondLightSource/daq-queuing-service/pull/69 resuming an empty queue is nonsensical. The UI should reflect this by not allowing the user to do it, with a tooltip as to why

# Acceptance Criteria
* If the queue is empty then you cannot resume it
* There is a tooltip explaining this e.g. "Cannot resume an empty queue, please queue something first"

Start by locating the UI control that resumes the queue and the existing empty-queue state. Check how disabled controls display tooltips, then verify that an empty queue cannot be resumed and shows the requested explanation, while non-empty queues retain the resume action.

Written by the indexing model from the issue text.