Make ResultProcessorBase destructor virtual so that derived classes have their destructors called.

Summary:
We create instances of `ResultProcessor` and `DummyResultProcessor`, but when they are destroyed they are pointers to `ResultProcessorBase`.
The non-virtual default destructor means the derived class destructor was not being called, potentially leaking memory.

Ref T57532

Reviewers: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, vladimirm

Reviewed By: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, vladimirm

Subscribers: vladimirm

Maniphest Tasks: T57532

Differential Revision: https://phabricator.sourcevertex.net/D62514

Author: jakeh-gc

tensorflow/compiler/plugin/poplar/kernels/application_runtime/application_runtime.cc

@@ -283,6 +283,8 @@ class IOConfig {
 // Base class which is used for processing the results from outfeed callbacks.
 class ResultProcessorBase {
  public:
+  virtual ~ResultProcessorBase() = default;
+
   // Returns whether all outputs have been processed.
   virtual bool ProcessOutput(const std::string& name, void* data) {
     // Check whether this is the last callback.