* Convert ID Integer columns to strings

Converts any ID (PK or FK) column that's derived from a :type/Integer to
a string in query middleware (at the end of query processing.)

JavaScript treats all numbers as floats, with a 52 bit mantissa. Any
integer larger than 52 bits ends up looking like a strange floating
point number.

This will allow the UI to properly display a number n where n > 2^52 or
n < -2^52

Resolves #5816

[ci all]

* code review feedback

* skip the reduce phase if there are no columns to update

* handle joins properly

joins have two :field-id values in them. handle them appropriately

* update cloverage build

* update tools.namespace for newer cloverage

* handle all query types more gracefully

Only in cases where we have an explicit :field-id do we try to do the
coercions to strings. It's important to not filter the :fields clause in
such a way that anything is left out - if they were, the keep-indexed
call would modify the wrong values in the result.