[7.17] [ML] Include an extra header in CDataFrameRowSlice (#2565)

Our two ARM macOS build servers have somehow ended up running
different versions of Xcode - one is running version 12 and the
other version 13.

There have been changes to the C++ standard library between
these versions that reveal a technical violation that we
were previously getting away with: CDataFrameRowSlice.cc uses
file streams without including the necessary header. Previously
it must have been indirectly included. This PR includes it
explicitly.

Backport of #2563

Author: David Roberts

include/model/CStringStore.h

@@ -23,6 +23,7 @@
 #include <atomic>
 #include <functional>
 #include <string>
+#include <vector>
 
 namespace CResourceMonitorTest {
 class CTestFixture;

lib/core/CDataFrameRowSlice.cc

@@ -20,6 +20,7 @@
 
 #include <boost/filesystem.hpp>
 
+#include <fstream>
 #include <memory>
 #include <vector>