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

compiler/testData/loadJava/compiledKotlin/prop/OverrideTraitVal.txt

@@ -6,7 +6,7 @@ internal open class Subclass : test.Trait {
         internal open override /*1*/ fun <get-shape>(): kotlin.String
 }
 
-internal trait Trait {
+internal interface Trait {
     internal abstract val shape: kotlin.String
         internal abstract fun <get-shape>(): kotlin.String
 }

compiler/testData/loadJava/compiledKotlin/prop/TraitFinalVar.txt

@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open var v: kotlin.String
         internal open fun <get-v>(): kotlin.String
         internal open fun <set-v>(/*0*/ value: kotlin.String): kotlin.Unit

compiler/testData/loadJava/compiledKotlin/prop/TraitOpenVal.txt

@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open val v: kotlin.String
         internal open fun <get-v>(): kotlin.String
 }

compiler/testData/loadJava/compiledKotlin/prop/VarDelegationToTraitImpl.txt

@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open var v: kotlin.String
         internal open fun <get-v>(): kotlin.String
         internal open fun <set-v>(/*0*/ value: kotlin.String): kotlin.Unit