Handle context receiver in KtModifierListOwner.addModifierList()

The existing `KtModifierListOwner.addModifierList(newModifierList)`
function adds a visibility keyword (e.g., `private`) in front of the
`context(..)` modifier, which generates wrong code. This commit fixes
it.

^KTIJ-23728 fixed

compiler/psi/src/org/jetbrains/kotlin/psi/addRemoveModifier.kt

@@ -16,7 +16,7 @@ import org.jetbrains.kotlin.psi.psiUtil.siblings
 private fun KtModifierListOwner.addModifierList(newModifierList: KtModifierList): KtModifierList {
     val anchor = firstChild!!
         .siblings(forward = true)
-        .dropWhile { it is PsiComment || it is PsiWhiteSpace }
+        .dropWhile { it is PsiComment || it is PsiWhiteSpace || it is KtContextReceiverList }
         .first()
     return addBefore(newModifierList, anchor) as KtModifierList
 }