Fix #[cfg(test)] methods in #[contractimpl] blocks failing to compile with testutils

[sisuresh]

Summary

When a pub fn inside a #[contractimpl] block is annotated with #[cfg(test)], the macro correctly propagates that attribute onto the generated __Contract__<method>__invoke_raw_slice function (via #(#attrs)* passthrough in derive_fn). However, derive_contract_function_registration_ctor only received method idents — not their attributes — so the generated registration ctor referenced __Contract__<method>__invoke_raw_slice unconditionally. In a non-test build with the testutils feature enabled, this produces:

error[E0425]: cannot find value `__Contract__persisted__invoke_raw_slice` in this scope

Fix

Change derive_contract_function_registration_ctor to accept (&Ident, &[Attribute]) pairs instead of just &Ident. For each method, extract any cfg attributes and emit them on the corresponding registration call in the ctor body, so #[cfg(test)] (and other cfg guards) are respected.

Impact

Narrow compile-time only: any crate with a #[cfg(test)] public method inside #[contractimpl] would fail to compile with testutils enabled. No runtime behavior is affected.

🤖 Generated with Claude Code

[sisuresh]

There's a PR that attempted to address this here - #1744