Extend import resolution for library-to-source analysis

Use composite importing scope for references when resolution anchors are enabled.
Composite scope provides additional descriptors from scope of resolution anchor module.
Overriding old importing scope with a new one is not possible as it breaks library
dependencies on other libraries, which are inaccessible in anchor scope (scope for sources).

KT-24309 In Progress

core/descriptors/src/org/jetbrains/kotlin/descriptors/findClassInModule.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.descriptors
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.resolve.RESOLUTION_ANCHOR_PROVIDER_CAPABILITY
+import org.jetbrains.kotlin.resolve.getResolutionAnchorIfAny
 
 fun ModuleDescriptor.findClassifierAcrossModuleDependencies(classId: ClassId): ClassifierDescriptor? = withAnchorFallback {
     val packageViewDescriptor = getPackage(classId.packageFqName)
@@ -40,7 +41,7 @@ fun ModuleDescriptor.findClassifierAcrossModuleDependencies(classId: ClassId): C
 private inline fun ModuleDescriptor.withAnchorFallback(
     crossinline doSearch: ModuleDescriptor.() -> ClassifierDescriptor? 
 ): ClassifierDescriptor? {
-    val anchor = getCapability(RESOLUTION_ANCHOR_PROVIDER_CAPABILITY)?.getResolutionAnchor(this)
+    val anchor = getResolutionAnchorIfAny()
     return if (anchor == null) doSearch() else doSearch() ?: anchor.doSearch()
 }
 

core/descriptors/src/org/jetbrains/kotlin/resolve/ResolutionAnchorProvider.kt

@@ -19,3 +19,6 @@ interface ResolutionAnchorProvider {
 }
 
 val RESOLUTION_ANCHOR_PROVIDER_CAPABILITY = ModuleCapability<ResolutionAnchorProvider>("ResolutionAnchorProvider")
+
+fun ModuleDescriptor.getResolutionAnchorIfAny(): ModuleDescriptor? =
+    getCapability(RESOLUTION_ANCHOR_PROVIDER_CAPABILITY)?.getResolutionAnchor(this)