replace 'trait' keyword with 'interface' in user-visible messages and code generation tools

compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/JvmOverloadWithNoDefaults.txt

@@ -1,4 +1,4 @@
-package 
+package
 
 internal final class C {
     kotlin.jvm.overloads() public constructor C()

compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnAbstractMethods.txt

@@ -8,7 +8,7 @@ internal abstract class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     kotlin.jvm.overloads() internal abstract fun foo(/*0*/ s: kotlin.String = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int

compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnPrivate.txt

@@ -1,4 +1,4 @@
-package 
+package
 
 internal fun foo(): kotlin.Unit