cleanup: remove dead code, fix bugs, refactor SSH dest parsing

- Remove debug printf calls from file.c
- Remove dead code: chunk_print, chunk_format, chunk_data_create/delete
- Remove unused config.use_single_send_per_file field
- Fix server_delete() no-op (double-pointer)
- Fix double cast (long)(long) -> ptrdiff_t in chunk.c
- Fix thread return value: thrd_error instead of 1
- Remove unused config param from receive_chunk_enqueue()
- Make queue_double_capacity() static
- Move SSH dest parsing into config.c as config_parse_ssh_dest()
- Fix test_config_ssh_dest to test parsing round-trip
- Remove chunk_format test (obsolete format)
- Replace chunk_data_delete with data_destroy in tests

src/shared/queue.h

@@ -17,7 +17,6 @@ Queue *queue_create(int capacity, void (*destroyer)(void *item));
 void queue_destroy(Queue *queue);
 bool queue_is_empty(Queue *queue);
 bool queue_is_full(Queue *queue);
-void queue_double_capacity(Queue *queue);
 void queue_enqueue(Queue *queue, void *item);
 void queue_enqueue_multithreaded(Queue *queue, void *item, mtx_t *mutex,
                                  cnd_t *condition_not_empty,