fix: skip formatting anonymous arguments

[andylokandy]

Closes #17

[Copilot]

Pull request overview

This PR attempts to fix the formatting of anonymous arguments in the logcall procedural macro, specifically addressing arguments generated by the async-trait crate. When async-trait transforms function signatures, it may rename underscore parameters (like _: String) to synthetic parameters starting with __arg. The change adds logic to skip these synthetic parameters when generating log format strings.

• Adds a check to skip arguments whose identifiers start with __arg prefix
• Converts identifier to string for prefix checking
• Adds test cases for functions with underscore parameters

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/lib.rs	Adds logic to skip async-trait generated parameters (those starting with "__arg") in the format string generation
tests/ui/ok/has-no-argument.rs	Adds test case for function with underscore parameter fn g(_: i32)
tests/ui/ok/async-trait-underscore.rs	Adds new test file for async-trait usage with underscore parameter in trait implementation

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