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/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/JvmOverloadFilter.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.resolve.jvm
 
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
+import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
 import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
 import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 import org.jetbrains.kotlin.fileClasses.NoResolveFileClassesProvider
@@ -40,12 +41,14 @@ object JvmOverloadFilter : OverloadFilter {
         }
 
         for (overload in overloads) {
+            if (overload is ConstructorDescriptor) continue
             if (overload !is DeserializedCallableMemberDescriptor) continue
 
             val containingDeclaration = overload.containingDeclaration
             if (containingDeclaration !is PackageFragmentDescriptor) {
                 throw AssertionError("Package member expected; got $overload with containing declaration $containingDeclaration")
             }
+
             val implClassName = JvmFileClassUtil.getImplClassName(overload) ?:
                                 throw AssertionError("No implClassName: $overload")
             val implClassFQN = containingDeclaration.fqName.child(implClassName)