Added an overloads option in completed-docs

[JoshuaKGoldberg]

PR checklist

• Addresses an existing issue: fixes completed-docs should have an option to check every method/function overload #4416
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

Opt-in (false by default) boolean flag that can be applied to functions and methods to require their overloads each receive their own documentation comment.

Also deleted a bunch of unnecessary tsconfig.json files that were still in the tests directory for completed-docs. I should have removed them when converting it to TypeScript.

CHANGELOG.md entry:

[new-rule-option] completed-docs: overloads option to enforce documentation of each overload signature

[JoshuaKGoldberg]

This assertion is unnecessary since it does not change the type of the expression. (no-unnecessary-type-assertion)
  593 |     }
  594 | 
> 595 |     return parent.getChildren()!;
      |           ^
  596 | }
  597 | 
  598 | function isGetAccessor(node: ts.Node): node is ts.GetAccessorDeclaration {

🤔

[adidahiya]

lgtm otherwise