Implementing interface (or abstract class) whose members reference a type included via a global import adds empty line to the beginning of file

Full issue information + repro project:
https://github.com/just-ero/roslyn-issues-repros/tree/main/5.0.0/003_ImplementInterface_ReturnTypeInGlobalUsings

Version

[!NOTE]
Roslyn: 5.0.0-1.25319.11
.NET SDK: 10.0.100-preview.5.25277.114

Visual Studio Code: 1.102.0
C# Extension: 2.84.19
C# Dev Kit Extension: 1.30.44

Steps to Reproduce

1. Add the following code in separate files:

   namespace N;
   
   class C;
   

   interface II
   {
       C M();
   }
   

   class Repro : II;
   

   Note: C must be in a different namespace than II, and Repro and Repro must not know of C before implemetation.
2. Add N to the global usings anywhere.
3. Apply the Implement interface quick fix to Repro.

Expected Behavior

No new line is added to the beginning of the file.

Actual Behavior

It is.

Speculation: this is possibly due to Roslyn making an attempt to add missing namespaces, but stopping after finding the global import.

Start with the linked repro project at 5.0.0/003_ImplementInterface_ReturnTypeInGlobalUsings and reproduce the issue by applying the Implement interface quick fix to Repro after adding N as a global using. Trace the Roslyn implementation of that quick fix and its namespace-import handling. Done means the generated implementation does not add an empty line at the beginning of the file, while the repro behavior is covered by a regression test.