Fix KT-10764 IDEA doesn't show overload conflict between constructor and function...

When checking for overloads in package, consider functions and top-level class constructors as possibly conflicting between each other. NB OverloadUtil uses containing package scope from module descriptor.

Change diagnostic message for CONFLICTING_OVERLOAD: it's misleading in case of fun vs constructor conflict.

Add custom multifile test for diagnostics in IDE (probably not the best; should preprocess file content if it's required to check highlighting in multiple files, not only in the first file).

Add test for KT-10765 Incremental compilation misses overload conflict between constructor and function ...

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -13083,6 +13083,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("FunVsCtorInDifferentFiles.kt")
+            public void testFunVsCtorInDifferentFiles() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/FunVsCtorInDifferentFiles.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("kt2418.kt")
             public void testKt2418() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/kt2418.kt");