[rocprofiler-register] Fix compilation with libc++ (#1241)

`tests/rocprofiler/rocprofiler.cpp` uses `std::string` without including `<string>` directly.
This works with libstdc++ due to transitive includes, but fails with libc++.

Closes #1240

projects/rocprofiler-register/tests/rocprofiler/rocprofiler.cpp

@@ -33,6 +33,7 @@
 #include <pthread.h>
 #include <sstream>
 #include <stdexcept>
+#include <string>
 #include <string_view>
 #include <tuple>
 #include <vector>