Go to definition of an extension declared in metadata leaves user at the top of the file.

**Version Used**:

**Steps to Reproduce**:

1. Call an extension declared in metadata
2. Go to the definition of the extension

I have provided a minimal reproduction in the linked repository. The file containing the extension calls is `Lib1/Class1.cs`

https://github.com/Arthri/demo-roslyn-extension-goto/

**Expected Behavior**: The user is brought to the file and line where the extension is declared.

**Actual Behavior**: The user is left at the top of the file where the extension is declared.

Start with the minimal reproduction in the linked repository and the extension calls in Lib1/Class1.cs. Reproduce Go to Definition for an extension declared in metadata, then trace the Roslyn navigation path responsible for the destination. Done means navigation opens the file at the extension's declaration line instead of leaving the user at the top of the file.

Written by the indexing model from the issue text.