Use struct for #audit_formula args

[samford]

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As discussed in #17643 (comment), adding type signatures to #audit_formula methods in formula cops would lead to verbose, repetitive signatures across the existing ~63 instances:

sig {
  override.params(
    _node:              RuboCop::AST::ClassNode,
    _class_node:        RuboCop::AST::ConstNode,
    _parent_class_node: RuboCop::AST::ConstNode,
    body_node:          RuboCop::AST::Node,
  ).void
}

This reworks #audit_formula to use a T::Struct for its arguments, which allows us to use a one-line signature for these methods. There may be room for improvement here but this seems to work as expected, at least.

[Bo98]

Not a fan of the name "args" as everything is an argument but otherwise don't have a strong opinion either way.

[dduugg]

Not a fan of the name "args" as everything is an argument but otherwise don't have a strong opinion either way.

I <3 this change, but agree that args could be improved. Maybe formula_nodes, if that seems an accurate description.

[MikeMcQuaid]

Thanks again @samford! Good to 🚢 once args renamed!

[samford]

I updated this to use FormulaNodes as the struct name and formula_nodes as the #audit_formula parameter name. Per Bo's comment, we can always rename it to something else if we ever add a non-node argument, so the "nodes" language seems fine for now (it's certainly more descriptive than args).

[MikeMcQuaid]

Looks great, thanks again!