Add query/search filter to queues

The use case: A JIRA service desk agent wants to search requests containing the text "Client abc".

Currently, they must either:

1. In the quick search field, type <Project Key> "client abc"
2. Open normal JIRA search and filter Project=<KEY> AND text ~ "Client abc"

This then takes them to search results for normal JIRA issues, and not the JIRA Service Desk. It is also annoying for the user to have to specify <Project Key> in all their searches.

Having a text filter - like the search on the Agile backlog screen - would be more sensible in this situation - especially for users less familiar with JIRA (eg Business sales support).

And no, we shouldn't expect all JIRA Service Desk users to be JIRA super-users: that's the whole point of Service Desk- to make the interface easier. Else, we may as well use normal JIRA + board?