Minor. Replace TraitImpl -> DefaultImpls, Trait -> Interface

There are still a lot of trait word entries in the source code,
only some of them got replaced here

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/CodegenUtil.kt

@@ -17,7 +17,7 @@
 package org.jetbrains.kotlin.backend.common
 
 import com.intellij.psi.PsiElement
-import org.jetbrains.kotlin.backend.common.bridges.findTraitImplementation
+import org.jetbrains.kotlin.backend.common.bridges.findInterfaceImplementation
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.psi.*
@@ -105,7 +105,7 @@ object CodegenUtil {
         for (declaration in DescriptorUtils.getAllDescriptors(descriptor.defaultType.memberScope)) {
             if (declaration !is CallableMemberDescriptor) continue
 
-            val traitMember = findTraitImplementation(declaration)
+            val traitMember = findInterfaceImplementation(declaration)
             if (traitMember == null || Visibilities.isPrivate(traitMember.visibility)) continue
 
             assert(traitMember.modality !== Modality.ABSTRACT) { "Cannot delegate to abstract trait method: $declaration" }

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/bridges/impl.kt

@@ -65,7 +65,7 @@ class DescriptorBasedFunctionHandle(
 
     override val isDeclaration: Boolean =
             descriptor.kind.isReal ||
-            findTraitImplementation(descriptor) != null
+            findInterfaceImplementation(descriptor) != null
 
     override val isAbstract: Boolean =
             descriptor.modality == Modality.ABSTRACT ||
@@ -88,7 +88,7 @@ class DescriptorBasedFunctionHandle(
  * trait implementation should be generated into the class containing the fake override; or null if the given function is not a fake
  * override of any trait implementation or such method was already generated into the superclass or is a method from Any.
  */
-fun findTraitImplementation(descriptor: CallableMemberDescriptor): CallableMemberDescriptor? {
+fun findInterfaceImplementation(descriptor: CallableMemberDescriptor): CallableMemberDescriptor? {
     if (descriptor.kind.isReal) return null
     if (isOrOverridesSynthesized(descriptor)) return null