feat: sort non keyword search results a-z

[LavMatt]

This PR addresses #798 and now search results when browsing by subject area or filtering will be sorted ascending rather than the default relevant ordering.

or in other words any results shown that are not the result of a keyword search query entered via the search input text box

I've also had to change the field name passed to the graphql searchAcrossEntities query's sort arg. If name is used it errors if no results are returned, but using _entityName is handled by the query and is consistent with how the datahub UI uses the query to sort search results

[murdo-moj]

A lot of this code looks left over from when we had more customisability on the sorting of results. Is there a bit of a tidy up of that code we can do since the sort option on the form doesn't do anything now?

[LavMatt]

A lot of this code looks left over from when we had more customisability on the sorting of results. Is there a bit of a tidy up of that code we can do since the sort option on the form doesn't do anything now?

I think we retain that because we have a waffle switch to enable us to turn sort radio buttons back on