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

compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/InheritParameterName.txt

@@ -2,11 +2,11 @@ package test
 
 public /*synthesized*/ fun A(/*0*/ function: (kotlin.Int) -> kotlin.Unit): test.A
 
-public trait A {
+public interface A {
     public abstract fun foo(/*0*/ p0: kotlin.Int): kotlin.Unit
 }
 
-internal trait B {
+internal interface B {
     internal abstract fun foo(/*0*/ kotlinName: kotlin.Int): kotlin.Unit
 }
 

compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/javaRefersToKotlin.txt

@@ -2,13 +2,13 @@ package test
 
 public /*synthesized*/ fun J(/*0*/ function: (test.K!) -> kotlin.Unit): test.J
 
-public trait J {
+public interface J {
     public abstract fun foo(/*0*/ p0: test.K!): kotlin.Unit
 }
 
-internal trait K {
+internal interface K {
 }
 
-internal trait K1 : test.J {
+internal interface K1 : test.J {
     public abstract override /*1*/ fun foo(/*0*/ k: test.K?): kotlin.Unit
 }

compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/propagationAgainstDeserializedSuperclass.txt

@@ -5,7 +5,7 @@ public open class J : test.K {
     public open override /*1*/ fun foo(/*0*/ l: kotlin.(Mutable)List<kotlin.String!>!): kotlin.String!
 }
 
-internal trait K {
+internal interface K {
     public abstract fun foo(/*0*/ l: kotlin.MutableList<kotlin.String>): kotlin.String
 }