[gwp_asan] Add missing <algorithm> include

[gulfem]

Summary

After https://reviews.llvm.org/D119667, <algorithm> is no longer
transitively included from various headers. This patch adds the
<algorithm> include into gwp_asan.

[phosek]

LGTM

[MaskRay]

Thanks! You may make such fixes without a review.

compiler-rt/lib/gwp_asan/tests/iterate.cpp

 //===-- iterate.cpp ---------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "gwp_asan/tests/harness.h"
 
+#include <algorithm>
 #include <set>
 #include <vector>
 
 TEST_F(CustomGuardedPoolAllocator, Iterate) {
   InitNumSlots(7);
   std::vector<std::pair<void *, size_t>> Allocated;
   auto alloc = [&](size_t size) {
     Allocated.push_back({GPA.allocate(size), size});