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

idea/testData/multiModuleHighlighting/hierarchicalExpectActualMatching/diamondDuplicateActuals/top/top.kt

@@ -1,5 +1,5 @@
 package sample
 
-expect class <!AMBIGUOUS_ACTUALS("Class 'A'", "bottom.kt, left.kt")!>A<!> {
-    fun <!AMBIGUOUS_ACTUALS("Function 'foo'", "bottom.kt, left.kt")!>foo<!>(): Int
+expect class <!AMBIGUOUS_ACTUALS("Class 'A'", "bottom, left")!>A<!> {
+    fun <!AMBIGUOUS_ACTUALS("Function 'foo'", "bottom, left")!>foo<!>(): Int
 }