K2 Scripting: fix script this receiver handling in IR

also fix accessor lowering

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/utils/FirScriptUtils.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2010-2023 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.declarations.utils
+
+const val SCRIPT_SPECIAL_NAME_STRING = "<script>"
+const val SCRIPT_RECEIVER_NAME_PREFIX = "\$script_receiver"