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/incompleteCodeNoNoneApplicable.txt

@@ -20,6 +20,4 @@ package
 public fun test(): kotlin.Unit
 
 package p {
-    public fun f(/*0*/ s: kotlin.String, /*1*/ t: kotlin.String): kotlin.String
-    public fun f(/*0*/ s: kotlin.String, /*1*/ t: kotlin.String): kotlin.String
 }