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/missingOverload/output.txt

@@ -5,7 +5,7 @@ Output:
 -- JVM --
 Exit code: COMPILATION_ERROR
 Output:
-compiler/testData/multiplatform/missingOverload/common.kt:7:13: error: expected function 'g' has no actual declaration in module
+compiler/testData/multiplatform/missingOverload/common.kt:7:13: error: expected function 'g' has no actual declaration in module <main>
 The following declaration is incompatible because parameter types are different:
     public actual fun g(a: Any): Unit