Deprecate debug buffer in Module

Pull Request resolved: #14161

It's in release 0.7 so following deprecation schedule.

debug_buffer is part of the event tracer, which is passed into Module. There isn't a public API on event tracer to set the debug_buffer, so the one held by Module is always empty.

Added in D71135352 for pybindings migration, however the debug buffer is held by PyModule in that case.
ghstack-source-id: 308829478
@exported-using-ghexport

Differential Revision: [D82125911](https://our.internmc.facebook.com/intern/diff/D82125911/)

Author: lucylq

extension/module/module.h

@@ -598,8 +598,9 @@ class Module {
     return event_tracer_.get();
   }
 
-  ET_NODISCARD
-  runtime::Span<uint8_t> debug_buffer() {
+  // Note: thie 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_;