Add cost info field to IODebugContext (#13666)

Summary:
This field will be used internally to feed Warm Storage cost information back through the Sally IO stack. This is needed for cost accounting / reporting.

Pull Request resolved: #13666

Test Plan: I made the additional changes needed to set/record the new cost info field, and confirmed that this information could be fed through.

Reviewed By: anand1976

Differential Revision: D76070434

Pulled By: archang19

fbshipit-source-id: 2fab975f14fd8f7c20b5d0d85c31686ccf682068

Author: archang19

include/rocksdb/file_system.h

@@ -18,6 +18,7 @@
 
 #include <stdint.h>
 
+#include <any>
 #include <chrono>
 #include <cstdarg>
 #include <functional>
@@ -250,6 +251,9 @@ struct IODebugContext {
   };
   uint64_t trace_data = 0;
 
+  // Arbitrary structure containing cost information about the IO request
+  std::any cost_info;
+
   IODebugContext() {}
 
   void AddCounter(std::string& name, uint64_t value) {