Do not update on progress more frequently than once in two seconds pe…

…r file or when done

This is primarily to resolve the problem of pyout "dragging us behind" which
slows down entire download process.

#1549

dandi/download.py

@@ -358,13 +358,34 @@ def download_generator(self) -> Iterator[dict]:
                         lock=lock,
                     )
 
+                def _progress_filter(gen):
+                    """To reduce load on pyout etc, make progress reports only if enough time
+                    from prior report has passed (over 2 seconds) or we are done (got 100%).
+
+                    Note that it requires "awareness" from the code below to issue other messages
+                    with bundling with done% reporting if reporting on progress of some kind (e.g.,
+                    adjusting "message").
+                    """
+                    prior_time = 0
+                    warned = False
+                    for rec in gen:
+                        current_time = time.time()
+                        if done_perc := rec.get("done%", 0):
+                            if isinstance(done_perc, (int, float)):
+                                if current_time - prior_time < 2 and done_perc != 100:
+                                    continue
+                            elif not warned:
+                                lgr.warning("Received non numeric done%: %r", done_perc)
+                        prior_time = current_time
+                        yield rec
+
                 # If exception is raised we might just raise it, or yield
                 # an error record
                 gen = {
                     "raise": _download_generator,
                     "yield": _download_generator_guard(path, _download_generator),
                 }[self.on_error]
-
+                gen = _progress_filter(gen)
                 if self.yield_generator_for_fields:
                     yield {"path": path, self.yield_generator_for_fields: gen}
                 else:
@@ -1247,9 +1268,9 @@ def feed(self, path: str, status: dict) -> Iterator[dict]:
                 self.files[path].downloaded = size
                 self.maxsize += size
             self.set_status(out)
-            yield out
             if self.zarr_size:
-                yield self.get_done()
+                out.update(self.get_done())
+            yield out
         elif keys == ["size"]:
             self.files[path].size = size
             self.maxsize += status["size"]
@@ -1274,11 +1295,11 @@ def feed(self, path: str, status: dict) -> Iterator[dict]:
                 self.files[path].state = DLState.ERROR
                 out = {"message": self.message}
                 self.set_status(out)
-                yield out
                 sz = self.files[path].size
                 if sz is not None:
                     self.maxsize -= sz
-                    yield self.get_done()
+                    out.update(self.get_done())
+                yield out
         elif keys == ["checksum"]:
             pass
         elif status == {"status": "setting mtime"}:
@@ -1287,6 +1308,7 @@ def feed(self, path: str, status: dict) -> Iterator[dict]:
             self.files[path].state = DLState.DONE
             out = {"message": self.message}
             self.set_status(out)
+            out.update(self.get_done())
             yield out
         else:
             lgr.warning(