Don't put back in the cruft we just took out

Where we had complex dependencies that now are unnecessary, simplify
them. Regenerate poetry.lock to track the result.

This commit addresses pylint alarms for instances of unbounded
`@lru_cache` decorators:

* In one instance, we merely silence the alarm; there is no structural
  way to address the concern. We believe the typical use pattern will be
  creation of a single scanner object that persists for nearly the life
  of execution, and therefore pylint's concerns regarding persistence of
  `self` references in the cache is not well-founded.

* In the other instance, we convert the function to a static method --
  it never referenced `self` anyway.