iwyu fixes for VS 16.7's STL

This lets us build with the STL from the new Visual Studio 16.7 release,
https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#16.7.0

Specifically, I think this is from STL updates,
https://github.com/microsoft/STL/wiki/Changelog#vs-2019-167

Probably this one,

    <array> no longer includes <algorithm>, <iterator>, and <tuple>; this is
    a source-breaking change for projects that weren't strict about
    including what they use. #482

Change-Id: Id95a7966c636b70b56522bc80e6daa626749e916
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308496
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/tests/OpChainTest.cpp b/tests/OpChainTest.cpp
index 3f8885e..a7c14cf 100644
--- a/tests/OpChainTest.cpp
+++ b/tests/OpChainTest.cpp
@@ -14,6 +14,7 @@
 #include "src/gpu/GrRecordingContextPriv.h"
 #include "src/gpu/ops/GrOp.h"
 #include "tests/Test.h"
+#include <iterator>
 
 // We create Ops that write a value into a range of a buffer. We create ranges from
 // kNumOpPositions starting positions x kRanges canonical ranges. We repeat each range kNumRepeats