Deprecate debug buffer in Module (#14199)

This PR was created by the merge bot to help merge the original PR into
the main branch.
ghstack PR number: #14161 by
@lucylq
^ Please use this as the source of truth for the PR details, comments,
and reviews
ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/lucylq/112/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/lucylq/112/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/main
Merge bot PR head:
https://github.com/pytorch/executorch/tree/gh/lucylq/112/orig
@diff-train-skip-merge

Co-authored-by: lucylq <[email protected]>

Author: pytorchbot

extension/module/module.h

@@ -598,8 +598,9 @@ class Module {
     return event_tracer_.get();
   }
 
-  ET_NODISCARD
-  runtime::Span<uint8_t> debug_buffer() {
+  // Note: this debug_buffer will always be empty. The one being used is in
+  // the event_tracer attached to module. Please use that one.
+  ET_DEPRECATED ET_NODISCARD runtime::Span<uint8_t> debug_buffer() {
     return runtime::Span<uint8_t>(debug_buffer_.data(), debug_buffer_.size());
   }
 
@@ -622,7 +623,7 @@ class Module {
   std::unique_ptr<runtime::EventTracer> event_tracer_;
   std::unique_ptr<runtime::DataLoader> data_map_loader_;
   std::unique_ptr<NamedDataMap> data_map_;
-  std::vector<uint8_t> debug_buffer_;
+  ET_DEPRECATED std::vector<uint8_t> debug_buffer_;
 
  protected:
   std::unordered_map<std::string, MethodHolder> methods_;