Add debug strings to frontend scopes-related structures

Such as:
- PackageFragmentProviders, and, in particular,
CompositePackageFragmentProviders
- JavaPackageFragments
- Scopes produced by those providers

The rationale is that a lot of frontend-facing bugs (like red code) are
easily recognizeable in resolution. But at that point you just see a
bunch of scopes, without meaningful toStrings, you don't know who has
produced them, and what's exactly wrong.

With this commit it should make debugging slightly easier: now at least
you'll be able to see that "this scope is a scope of package fragment
for foo.bar of module baz" and decide whether the declaration should or
should not have been resolved from such scope.

compiler/util-klib-metadata/src/org/jetbrains/kotlin/library/metadata/KlibMetadataPackageFragment.kt

@@ -94,10 +94,9 @@ abstract class KlibMetadataPackageFragment(
             nameResolver,
             KlibMetadataVersion.INSTANCE,
             /* containerSource = */ null,
-            components
-        ) {
-            loadClassNames()
-        }
+            components,
+            "scope for $this"
+        ) { loadClassNames() }
     }
 
     override fun getMemberScope(): DeserializedPackageMemberScope = _memberScope

compiler/util-klib-metadata/src/org/jetbrains/kotlin/library/metadata/impl/KlibMetadataModuleDescriptorFactoryImpl.kt

@@ -183,7 +183,10 @@ class KlibMetadataModuleDescriptorFactoryImpl(
         }
 
         return compositePackageFragmentAddend?.let {
-            CompositePackageFragmentProvider(listOf(it, provider))
+            CompositePackageFragmentProvider(
+                listOf(it, provider),
+                "CompositeProvider@KlibMetadataModuleDescriptorFactory for $moduleDescriptor"
+            )
         } ?: provider
     }