[FIR] Extract LHS receiver of assignment operator statements

#KT-53490 Fixed

compiler/testData/codegen/box/operatorConventions/reassignmentLhsCaching.kt

@@ -0,0 +1,60 @@
+// EXPECTED_REACHABLE_NODES: 1298
+package foo
+
+var log = ""
+
+class A(val value: Int) {
+    operator fun plus(other: A): A {
+        log += "A.plus(${other.value});"
+        return A(value + other.value)
+    }
+}
+
+val _array = arrayOf(A(2))
+
+fun getArray(): Array<A> {
+    log += "getArray();"
+    return _array
+}
+
+fun getArrayIndex(): Int {
+    log += "getArrayIndex();"
+    return 0
+}
+
+class B(value: Int) {
+    var a = A(value)
+}
+
+val _property = B(10)
+val _functionResult = B(100)
+
+val foo: B
+    get() {
+        log += "foo;"
+        return _property
+    }
+
+fun bar(): B {
+    log += "bar();"
+    return _functionResult
+}
+
+fun box(): String {
+    getArray()[getArrayIndex()] += A(3)
+    assertEquals(5, _array[0].value)
+
+    foo.a += A(20)
+    assertEquals(30, _property.a.value)
+
+    bar().a += A(200)
+    assertEquals(300, _functionResult.a.value)
+
+    assertEquals("getArray();getArrayIndex();A.plus(3);foo;A.plus(20);bar();A.plus(200);", log)
+
+    return "OK"
+}
+
+fun assertEquals(first: Any?, second: Any?) {
+    if (first != second) throw AssertionError("$first != $second")
+}