N occurrences of a parameterized string.   This allows parameterized
warnings that can refer to their arguments to be delivered a fixed
number of times until allowing Python warning filters to squelch them,
and prevents memory from growing unbounded within Python's
warning registries.
fixes #3178

- an existing state shouldn't need its load_options/load_path updated;
it should maintain those from its original Query source.  there's no
tests that check this behavior

that I'd like to start de-inlining again in the hopes of making this readable.

- inline the column-based expiration operations as well

instances(), using a named tuple it can assign to directly.  this way
we never have to worry about that structure changing anymore, though
we are still having it append (key, fn) which is kind of awkward.
- inline _populators() into instance(), it's a little verbose but
saves an fn call

if a load() or refresh() event changes history (which...why...but anyway)
the state of the object is the same; currently it seems that history
gets reset but on a refresh, the object still goes into session.dirty
- simplify what we store in partials