Rename Arguments to Parameters in the AST (#6253)

## Summary

This PR renames a few AST nodes for clarity:

- `Arguments` is now `Parameters`
- `Arg` is now `Parameter`
- `ArgWithDefault` is now `ParameterWithDefault`

For now, the attribute names that reference `Parameters` directly are
changed (e.g., on `StmtFunctionDef`), but the attributes on `Parameters`
itself are not (e.g., `vararg`). We may revisit that decision in the
future.

For context, the AST node formerly known as `Arguments` is used in
function definitions. Formally (outside of the Python context),
"arguments" typically refers to "the values passed to a function", while
"parameters" typically refers to "the variables used in a function
definition". E.g., if you Google "arguments vs parameters", you'll get
some explanation like:

> A parameter is a variable in a function definition. It is a
placeholder and hence does not have a concrete value. An argument is a
value passed during function invocation.

We're thus deviating from Python's nomenclature in favor of a scheme
that we find to be more precise.

crates/ruff_python_formatter/src/other/mod.rs

@@ -1,7 +1,4 @@
 pub(crate) mod alias;
-pub(crate) mod arg;
-pub(crate) mod arg_with_default;
-pub(crate) mod arguments;
 pub(crate) mod comprehension;
 pub(crate) mod decorator;
 pub(crate) mod elif_else_clause;
@@ -9,4 +6,7 @@ pub(crate) mod except_handler_except_handler;
 pub(crate) mod identifier;
 pub(crate) mod keyword;
 pub(crate) mod match_case;
+pub(crate) mod parameter;
+pub(crate) mod parameter_with_default;
+pub(crate) mod parameters;
 pub(crate) mod with_item;