Add Check for Non-accessible Code at Analyzer

[nytian]

fix Azure/azure-functions-durable-extension#3173

Analyzer threw ArgumentException and AD0001 warning when encountering extension methods defined in separate projects/assemblies.

This PR add checks to skip analyzing methods for non-accessible source code

[Copilot]

Pull request overview

This PR fixes a bug where the analyzer throws ArgumentException and generates AD0001 warnings when encountering extension methods or other types defined in external assemblies without available source code. The fix adds defensive checks to verify that syntax references are available before attempting to access them.

Key Changes:

• Added IsEmpty check in GetSyntaxNodes to return empty enumerable for methods without syntax references
• Added IsEmpty check in OrchestrationAnalyzer before accessing method syntax for Func orchestrators

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Analyzers/RoslynExtensions.cs	Added defensive check in GetSyntaxNodes to return empty when no syntax references exist
src/Analyzers/Orchestration/OrchestrationAnalyzer.cs	Added check before accessing syntax references for method reference operations in Func orchestrators

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[Copilot]

This fix prevents ArgumentException when analyzing extension methods from external assemblies, but there doesn't appear to be test coverage for this scenario. Consider adding a test case that includes an orchestration calling an extension method defined in a separate assembly to ensure this fix works as expected and to prevent regression.