APICompat not catching extracting a method from interface to 'base' interface

### Describe the bug
The actual case here: https://github.com/dotnet/msbuild/pull/10771/files#diff-b60043ef00b4fe23265f682a6b55b234e9bd2d191167475e8d2699a1c4b8ca02R17

What was done - a single memeber from `IInterface` was copied to `IBase` and that interface was added as base `IInterface`.

**Before:**
```
IInterface
{
string A { get; }
string B { get; }
}
```

**After:**
```
IBase
{
string A { get; }
}

IInterface: IBase
{
new string A { get; }
string B { get; }
}
```

This is not breaking implicit implementors of `IInterface`, but will break explicit implementors.

### Expected behavior

Api compat flags such refactoring

### Actual behavior

Change is not flaged