Allow setting restic --limit-upload and ---limit-download

[Eldiabolo21]

Describe the feature you'd like to have.
It would be great if the restic mover supported speed limits. Especially for inital backups that take longer, it shouldn't hog all the upload bandwidth.

What is the value to the end user? (why is it a priority?)
Users can more granuarly decided how restic should work.

How will we know we have a good solution? (acceptance criteria)
Config options are passed directly to restic and make use of the options that are already present there.

Additional context
Maybe build the feature in such a way, that additional options can be passed in a general way ?!

[tesshuflower]

It doesn't look like limit-upload and limit-download are currently available to set as env vars in restic - if that were the case it would be much easier to pass through in a general way (i.e. via the restic secret).

Any interest in bringing this forward to restic? I'm not sure how they decide which command line arguments get set via env var vs which ones are not.