IR: move UniqId to ir.tree module

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/UniqId.kt

@@ -0,0 +1,15 @@
+package org.jetbrains.kotlin.ir.util
+
+// This is an abstract uniqIdIndex any serialized IR declarations gets.
+// It is either isLocal and then just gets and ordinary number within its module.
+// Or is visible across modules and then gets a hash of mangled name as its index.
+
+inline class UniqId(val index: Long) {
+    val isPublic: Boolean get() = (index and (1L shl 63)) != 0L
+    val isLocal: Boolean get() = (index and (1L shl 63)) == 0L
+
+    companion object {
+        val NONE = UniqId(0x7fffffffL)
+    }
+}
+