Use modules instead of files for MPP diagnostic

Using files turned to be a bad idea, because people often
use the same name for files with expects and with corresponding actuals.

This commits disambiguiates ambiguous message for
AMBIGUOUS_ACTUALS/AMBGIUOUS_EXPECTS diagnostics by using modules instead
of files

^KT-32582 Fixed

compiler/testData/multiplatform/incompatibleClasses/output.txt

@@ -5,19 +5,19 @@ Output:
 -- JVM --
 Exit code: COMPILATION_ERROR
 Output:
-compiler/testData/multiplatform/incompatibleClasses/common.kt:14:16: error: expected class 'C1' has no actual declaration in module
+compiler/testData/multiplatform/incompatibleClasses/common.kt:14:16: error: expected class 'C1' has no actual declaration in module <main>
 The following declaration is incompatible because number of type parameters is different:
     public final actual class C1<A, Extra>
 
 expect class C1<A>
                ^
-compiler/testData/multiplatform/incompatibleClasses/common.kt:16:16: error: expected class 'C3' has no actual declaration in module
+compiler/testData/multiplatform/incompatibleClasses/common.kt:16:16: error: expected class 'C3' has no actual declaration in module <main>
 The following declaration is incompatible because upper bounds of type parameters are different:
     public final actual class C3<D, E : D?>
 
 expect class C3<D, E : D>
                ^
-compiler/testData/multiplatform/incompatibleClasses/common.kt:18:16: error: expected class 'C4' has no actual declaration in module
+compiler/testData/multiplatform/incompatibleClasses/common.kt:18:16: error: expected class 'C4' has no actual declaration in module <main>
 The following declaration is incompatible because upper bounds of type parameters are different:
     public actual typealias C4<F> = C4Impl<F>