message: Use ParametersSpec::with_capacity in #[starlark_module]
  Summary: Should slightly reduce reallocations
diff: @@ -64,7 +64,7 @@ use syn::*;
  // }
  // {
  // #[allow(unused_mut)]
  -// let mut signature = starlark::eval::ParametersSpec::new("cc_binary".to_owned());
  +// let mut signature = starlark::eval::ParametersSpec::with_capcity("cc_binary".to_owned(), 2);
  // signature.required("name");
  // signature.required("srcs");
  // globals_builder.set(
  @@ -226,6 +226,7 @@ fn add_function(func: &ItemFn) -> proc_macro2::TokenStream {
  };
  let body = &func.block;
  let args = func.sig.inputs.iter().map(Arg::new).collect::<Vec<_>>();
  + let args_count = args.len();
  let bind_args = args.map(bind_argument);
  let signature = args.map(record_argument);
  let setter = if is_attribute {
  @@ -280,7 +281,7 @@ fn add_function(func: &ItemFn) -> proc_macro2::TokenStream {
  }
  {
  #[allow(unused_mut)]
  - let mut signature = starlark::eval::ParametersSpec::new(#name_str.to_owned());
  + let mut signature = starlark::eval::ParametersSpec::with_capacity(#name_str.to_owned(), #args_count);
  #( #signature )*
  #setter
  }
  