[K/N] Extracted some common BitSet utils

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/BitSetUtil.kt

@@ -0,0 +1,19 @@
+/*
+ * 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.backend.common
+
+import java.util.*
+
+fun BitSet.copy() = BitSet(this.size()).apply { this.or(this@copy) }
+
+inline fun BitSet.forEachBit(block: (Int) -> Unit) {
+    var i = -1
+    while (true) {
+        i = nextSetBit(i + 1)
+        if (i < 0) break
+        block(i)
+    }
+}