Fix trait method call resolution in contractimpl

[leighmcculloch]

What

Use fully qualified syntax (<Type as Trait>::func()) in macro-generated WASM exports when #[contractimpl] is applied to a trait impl block.

Why

Rust's name resolution prefers inherent methods over trait methods when using <Type>::func() syntax. If a contract type has both an inherent method and a trait method with the same name, the generated export incorrectly calls the inherent method instead of the trait method the #[contractimpl] block is defined for.

[Copilot]

Pull request overview

This PR fixes #[contractimpl] macro-generated WASM exports for trait impl blocks so they reliably call the intended trait function (rather than an inherent function with the same name) by switching to UFCS (<Type as Trait>::func).

Changes:

• Update macro function-call generation to use UFCS when #[contractimpl] is applied to impl Trait for Type.
• Add a regression test exercising a trait/inherent name collision and asserting the trait method is called.
• Add a corresponding test snapshot and register the new test module.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
soroban-sdk-macros/src/derive_fn.rs	Generates UFCS calls for trait impl exports to fix Rust name-resolution behavior.
soroban-sdk/src/tests/contractimpl_trait_call_resolution.rs	Adds regression test for trait vs inherent associated function call resolution.
soroban-sdk/src/tests.rs	Registers the new test module.
soroban-sdk/test_snapshots/tests/contractimpl_trait_call_resolution/calls_trait_fn.1.json	Adds the expected snapshot output for the new regression test.