Document areas of code complexity

[cclauss]

As discussed at #2360 (review), let's set upper limits on or at least document code complexity.

Ruff provides one McCabe metric and four Pylint refactor metrics (even more in --preview mode).

This pull request shows three ways to document where code complexity exists.

1. noqa plus a few lines in the docstring. (Semi-automated generation with a script.)
2. Just noqa.
3. tool.ruff.lint.per-file-ignores in pyproject.toml

On the main branch...

% ruff check --select=C90,PLR09 --statistics

22	PLR0913	too-many-arguments
17	C901   	complex-structure
16	PLR0912	too-many-branches
13	PLR0915	too-many-statements
 2	PLR0911	too-many-return-statements

% ruff check --select=C90,PLR09 --statistics --preview

22	PLR0913	too-many-arguments
22	PLR0917	too-many-positional-arguments
17	C901   	complex-structure
16	PLR0912	too-many-branches
13	PLR0915	too-many-statements
10	PLR0914	too-many-locals
 5	PLR0916	too-many-boolean-expressions
 2	PLR0911	too-many-return-statements

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.16%. Comparing base (c8ab4a5) to head (8ca46a8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2370   +/-   ##
=======================================
  Coverage   99.16%   99.16%           
=======================================
  Files          40       40           
  Lines        3101     3101           
  Branches      680      680           
=======================================
  Hits         3075     3075           
  Misses         15       15           
  Partials       11       11