util: introduce helper AnyPtr to access std::any instances

Co-authored-by: Russell Yanofsky <russ@yanofsky.org>

src/util/system.h

@@ -25,6 +25,7 @@
 #include <util/threadnames.h>
 #include <util/time.h>
 
+#include <any>
 #include <exception>
 #include <map>
 #include <optional>
@@ -500,6 +501,18 @@ inline void insert(std::set<TsetT>& dst, const Tsrc& src) {
     dst.insert(src.begin(), src.end());
 }
 
+/**
+ * Helper function to access the contained object of a std::any instance.
+ * Returns a pointer to the object if passed instance has a value and the type
+ * matches, nullptr otherwise.
+ */
+template<typename T>
+T* AnyPtr(const std::any& any) noexcept
+{
+    T* const* ptr = std::any_cast<T*>(&any);
+    return ptr ? *ptr : nullptr;
+}
+
 #ifdef WIN32
 class WinCmdLineArgs
 {