Better user feedback during slow backend migrations (#2952)

* Better user feedback during slow backend migrations

This uses a tqdm progress bar to keep the user updated on the progress of the migrations.

I didn't realise this was necessary until I did a migration from Mongo to Postgres on CASE, and it took quite a long time to complete, I started to doubt that it was actually making progress.

Also includes a utility to help with tqdm in slow asynchronous for-loops.

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

* Make `async_tqdm` support async-for loops

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

* Reformat

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

* Remove unused method

* Remove quotes for the return type annotation

* Few style improvements

Co-authored-by: jack1142 <6032823+jack1142@users.noreply.github.com>

redbot/core/drivers/base.py

@@ -2,6 +2,8 @@ import abc
 import enum
 from typing import Tuple, Dict, Any, Union, List, AsyncIterator, Type
 
+from redbot.core.utils._internal_utils import async_tqdm
+
 __all__ = ["BaseDriver", "IdentifierData", "ConfigCategory"]
 
 
@@ -280,12 +282,23 @@ class BaseDriver(abc.ABC):
 
         """
         # Backend-agnostic method of migrating from one driver to another.
-        async for cog_name, cog_id in cls.aiter_cogs():
+        cogs_progress_bar = async_tqdm(
+            (tup async for tup in cls.aiter_cogs()),
+            desc="Migration progress",
+            unit=" cogs",
+            bar_format="{desc}: {n_fmt}{unit} [{elapsed},{rate_noinv_fmt}{postfix}]",
+            leave=False,
+            dynamic_ncols=True,
+            miniters=1,
+        )
+        async for cog_name, cog_id in cogs_progress_bar:
+            cogs_progress_bar.set_postfix_str(f"Working on {cog_name}...")
             this_driver = cls(cog_name, cog_id)
             other_driver = new_driver_cls(cog_name, cog_id)
             custom_group_data = all_custom_group_data.get(cog_name, {}).get(cog_id, {})
             exported_data = await this_driver.export_data(custom_group_data)
             await other_driver.import_data(exported_data, custom_group_data)
+        print()
 
     @classmethod
     async def delete_all_data(cls, **kwargs) -> None: