Module marked with ModuleSuffix attribute is hidden by another module with the same name

If a project contains two modules with the same name, one of which is marked with `ModuleSuffix` attribute:

```fsharp
// Foo1.fs
namespace Library

[]
module Foo =
let bar x = x
```
```fsharp
// Foo2.fs
module Library.Foo

let buzz x = x
```
symbols defined in the marked with `ModuleSuffix` attribute one are not seen in projects referencing this one:



The bug (feature?) was found while moving ExtCore library to .NET Standard 2.0

Minimal repro https://github.com/vasily-kirichenko/TwoModulesBug

It's compiled to (ILSpy):

```csharp
namespace Library
{
[CompilationMapping(SourceConstructFlags.Module)]
public static class Foo
{
public static a buzz(a x)
{
return x;
}
}
}

namespace Library
{
[CompilationMapping(SourceConstructFlags.Module), CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)]
public static class FooModule
{
public static a bar(a x)
{
return x;
}
}
}
```