[libc++][NFC] Remove test/support/tracked_value.h

[jloser]

Summary

No tests are using libcxx/test/support/tracked_value.h. So, remove it.

If CI passes, I'll land this.

[ldionne]

This LGTM, but please ensure you wait for a libc++ approval before committing -- just as a matter of process.

libcxx/test/support/tracked_value.h

-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-#ifndef SUPPORT_TRACKED_VALUE_H
-#define SUPPORT_TRACKED_VALUE_H
-
-#include <cassert>
-
-#include "test_macros.h"
-
-struct TrackedValue {
-    enum State { CONSTRUCTED, MOVED_FROM, DESTROYED };
-    State state;
-
-    TrackedValue() : state(State::CONSTRUCTED) {}
-
-    TrackedValue(TrackedValue const& t) : state(State::CONSTRUCTED) {
-        assert(t.state != State::MOVED_FROM && "copying a moved-from object");
-        assert(t.state != State::DESTROYED  && "copying a destroyed object");
-    }
-
-#if TEST_STD_VER >= 11
-    TrackedValue(TrackedValue&& t) : state(State::CONSTRUCTED) {
-        assert(t.state != State::MOVED_FROM && "double moving from an object");
-        assert(t.state != State::DESTROYED  && "moving from a destroyed object");
-        t.state = State::MOVED_FROM;
-    }
-#endif
-
-    TrackedValue& operator=(TrackedValue const& t) {
-        assert(state != State::DESTROYED && "copy assigning into destroyed object");
-        assert(t.state != State::MOVED_FROM && "copying a moved-from object");
-        assert(t.state != State::DESTROYED  && "copying a destroyed object");
-        state = t.state;
-        return *this;
-    }
-
-#if TEST_STD_VER >= 11
-    TrackedValue& operator=(TrackedValue&& t) {
-        assert(state != State::DESTROYED && "move assigning into destroyed object");
-        assert(t.state != State::MOVED_FROM && "double moving from an object");
-        assert(t.state != State::DESTROYED  && "moving from a destroyed object");
-        state = t.state;
-        t.state = State::MOVED_FROM;
-        return *this;
-    }
-#endif
-
-    ~TrackedValue() {
-        assert(state != State::DESTROYED && "double-destroying an object");
-        state = State::DESTROYED;
-    }
-};
-
-#endif // SUPPORT_TRACKED_VALUE_H