Handle Exceptions when saving attachments

[Cephian]

Running !list on spotty internet, the download can time out and give an unhandled TimeoutError. We may even want to notify the user in Discord that some files failed to download when the list appears

Interestingly, Nextcord documentation claims that Attachment.save() will only raise either nextcord.HttpException or nextcord.NotFound, so this might be case of lacking documentation on their part as well.

Task exception was never retrieved
future: <Task finished name='Task-45' coro=<scrape_channel_media.<locals>.dl_file() done, defined at /home/jack/Repos/busty/main
Traceback (most recent call last):
  File "/home/jack/Repos/busty/main.py", line 722, in dl_file
    await attachment.save(attachment_filepath)
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/nextcord/message.py", line 225, in save
    data = await self.read(use_cached=use_cached)
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/nextcord/message.py", line 267, in read
    data = await self._http.get_from_cdn(url)
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/nextcord/http.py", line 359, in get_from_cdn
    return await resp.read()
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/aiohttp/client_reqrep.py", line 1036, in read
    self._body = await self.content.read()
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/aiohttp/streams.py", line 375, in read
    block = await self.readany()
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/aiohttp/streams.py", line 397, in readany
    await self._wait("readany")
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/aiohttp/streams.py", line 303, in _wait
    with self._timer:
  File "/home/jack/Repos/busty/env/lib/python3.10/site-packages/aiohttp/helpers.py", line 721, in __exit__
    raise asyncio.TimeoutError from None
asyncio.exceptions.TimeoutError