[FE 1.0] Don't report UNUSED_* warnings on local properties with delegate

^KT-25527 Fixed

compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.fir.kt

@@ -0,0 +1,40 @@
+// ISSUE: KT-25527
+
+import kotlin.reflect.KProperty
+
+fun test_1(delegate: Delegate) {
+    var p1 by delegate
+    p1 = 10
+
+    var p2 by delegate
+    p2++
+
+    var p3 by delegate
+    ++p3
+}
+
+fun test_2() {
+    var p1 = 0
+    p1 = 10
+
+    var p2: Int
+    p2 = 10
+
+    var p3 = 1
+    p3++
+
+    var p4 = 1
+    ++p4
+}
+
+class Delegate {
+    var prop: Int = 0
+
+    operator fun getValue(thisRef: Any?, property: KProperty<*>): Int {
+        return prop
+    }
+
+    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Int) {
+        prop = value
+    }
+}