DB Backend: use new `TransactableHandle` types
Created by: camdencheek
This updates tests to use the new TransactableHandle
types and starts
migrating other code to use them. It renames NewHandleWithDB
to
NewHandleWithUntypedDB
and creates a new constructor NewHandleWithDB
that takes a *sql.DB
directly. Then, where the change is trivial, it
callers of NewHandleWithUntypedDB
to use NewHandleWithDB
instead. I
will make followup PRs to clean up remaining call sites.
Test plan
I converted tests for the old transaction code to use the new transaction types and everything passed.