Do not render declarations from other modules in diagnostic tests

Because PackageViewDescriptor may consist of several package fragments from
different modules (see LazyPackageViewDescriptorImpl#fragments), we now filter
out fragments from irrelevant modules before rendering them into the .txt

compiler/testData/diagnostics/tests/multimodule/duplicateMethod/extensionMatch.txt

@@ -17,10 +17,6 @@ package
 
 package p {
 
-    public interface B {
-        // -- Module: <m1> --
-    }
-
     public final class C : p.B {
         public constructor C()
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -51,12 +47,4 @@ package
 public fun p.B.test(): kotlin.Unit
 
 package p {
-
-    public interface B {
-        // -- Module: <m3> --
-    }
-
-    public final class C : p.B {
-        // -- Module: <m2> --
-    }
 }