Fix ICE in BuildDisposableCleanup when Dispose extension methods are in scope

[Copilot]

BuildDisposableCleanup crashes with an ICE ("Couldn't find Dispose on IDisposable, or it was overloaded") when a C#-style Dispose extension method is in scope alongside the intrinsic IDisposable.Dispose.

openSystemopenSystem.Runtime.CompilerServicestypeDisposable()=interface IDisposable withmember_.Dispose()=()[<Extension>]typePublicExtensions=[<Extension>]static member inlineDispose(this:#IDisposable)= this
letfoo()=use a =new Disposable()// ICE here()

Cause

The lookup uses TryFindIntrinsicOrExtensionMethInfo with ResultCollectionSettings.AllResults, which collects both intrinsic and extension methods. The subsequent | [x] -> x match fails when >1 candidate is returned.

Fix

Switch to ResultCollectionSettings.AtMostOneResult. This leverages the existing priority mechanism in AllMethInfosOfTypeInScope — when intrinsic methods are found, extension methods are skipped. Same priority rules as a hand-written (x :> IDisposable).Dispose() call.

[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