[FIR] Use optimized stdlib version of reversed list

compiler/fir/cones/src/org/jetbrains/kotlin/fir/util/Collections.kt

@@ -1,15 +0,0 @@
-/*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir.util
-
-private open class FrozenReversedListReadOnly<out T>(
-    private val delegate: List<T>
-) : AbstractList<T>() {
-    override val size: Int = delegate.size
-    override fun get(index: Int): T = delegate[size - 1 - index]
-}
-
-fun <T> List<T>.asReversedFrozen(): List<T> = FrozenReversedListReadOnly(this)