K1: Place integer cinterop conversions under a language feature

Note that it's quite hard to emit a particular diagnostic as
 type check happens later, after the conversion

 ^KT-56583

core/descriptors/src/org/jetbrains/kotlin/resolve/constants/CompileTimeConstant.kt

@@ -57,7 +57,8 @@ interface CompileTimeConstant<out T> {
         val isUnsignedLongNumberLiteral: Boolean,
         val usesVariableAsConstant: Boolean,
         val usesNonConstValAsConstant: Boolean,
-        // `isConvertableConstVal` means that this is `const val` that has `ImplicitIntegerCoercion` annotation
+        // `isConvertableConstVal` means that this is `const val` that can participate in signed to unsigned conversion
+        // see LanguageFeature.ImplicitSignedToUnsignedIntegerConversion
         val isConvertableConstVal: Boolean
     )