Fix StartDebuggingRequestHandler/ReplModeRequestHandler in lldb-dap (#104824)

`SBCommand::AddCommand()` requires `SBCommandPluginInterface` to be heap
based because it will be stored inside
`std::shared_ptr<lldb::SBCommandPluginInterface>` later for reference
counting. But lldb-dap passes
`StartDebuggingRequestHandler/ReplModeRequestHandler` static function
pointer to it which will cause corruption later during destruction.

This PR fixes this issue by making these two handler heap based.

Co-authored-by: jeffreytan81 <jeffreytan@fb.com>

Author: jeffreytan81

lldb/tools/lldb-dap/DAP.h

@@ -192,8 +192,6 @@ struct DAP {
   std::mutex call_mutex;
   std::map<int /* request_seq */, ResponseCallback /* reply handler */>
       inflight_reverse_requests;
-  StartDebuggingRequestHandler start_debugging_request_handler;
-  ReplModeRequestHandler repl_mode_request_handler;
   ReplMode repl_mode;
   std::string command_escape_prefix = "`";
   lldb::SBFormat frame_format;

lldb/tools/lldb-dap/lldb-dap.cpp

@@ -1627,12 +1627,12 @@ void request_initialize(const llvm::json::Object &request) {
       "lldb-dap", "Commands for managing lldb-dap.");
   if (GetBoolean(arguments, "supportsStartDebuggingRequest", false)) {
     cmd.AddCommand(
-        "startDebugging", &g_dap.start_debugging_request_handler,
+        "startDebugging", new StartDebuggingRequestHandler(),
         "Sends a startDebugging request from the debug adapter to the client "
         "to start a child debug session of the same type as the caller.");
   }
   cmd.AddCommand(
-      "repl-mode", &g_dap.repl_mode_request_handler,
+      "repl-mode", new ReplModeRequestHandler(),
       "Get or set the repl behavior of lldb-dap evaluation requests.");
 
   g_dap.progress_event_thread = std::thread(ProgressEventThreadFunction);