feat: add mssql adapter - #29

…terpolated N+1s

Follow-up to #29. Three things the adapter was missing:

- `parameterValues()` returned `[]` for a request with no `.input()` calls.
  A scope tells an N+1 apart from a statement that merely runs twice by
  watching the values vary, and falls back to the raw SQL only when the driver
  reports *no* parameters — so `[]` handed it a discriminator that was
  identical on every iteration. A loop building its SQL by interpolation, which
  is the code most likely to have an N+1 in it, was never reported. It now
  returns undefined when nothing was bound.
- `Request.prototype.batch()` was not patched, so a T-SQL batch went unseen.
- `PreparedStatement` was not patched. Executing one in a loop is an N+1 that
  costs less per iteration and is therefore easier to miss. The statement is
  captured at `prepare()` rather than read off an internal property, so a
  rename in the driver cannot silently break it.