Improve implied argument names

[kerams]

Description

Continuation of #15277, filling a remaining gap.

type Combine = delegate of first: int * second: int * third: int * fourth: int -> int

[<System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.NoInlining)>]
let f a b c d e g = a + b + c + d + e + g

let test1 = Combine(f 1 2)

Before

internal static class test1@6
{
    internal static int Invoke(int delegateArg0, int delegateArg1, int delegateArg2, int delegateArg3)
    {
        return f(1, 2, delegateArg0, delegateArg1, delegateArg2, delegateArg3);
    }
}

After

internal static class test1@6
{
    internal static int Invoke(int first, int second, int third, int fourth)
    {
        return f(1, 2, first, second, third, fourth);
    }
}

Checklist

• Test cases added
• Performance benchmarks added in case of performance changes
• Release notes entry updated

[github-actions]

❗ Release notes required

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---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/11.0.100.md
LanguageFeatures.fsi	docs/release-notes/.Language/preview.md

[github-actions]

🔍 Tooling Safety Check — Affects-Compiler-Output
Affects-Compiler-Output: modifies MethodCalls.fs changing emitted delegate argument names in IL

Generated by PR Tooling Safety Check · opus46 4.8M · ◷