Add AIFS ensembles

[karlwx]

Here's my first try. I added support for a product_suffix keyword argument in the AIFS template to allow users to grab the control run if they want. Example usage is in the notebook!

[williamhobbs]

This is great!

Adding a bullet for AIFS ens data availability at the beginning of the docs notebook might be helpful.

Tagging #454.

[blaylockbk]

I like it!

I wonder if a simple bool would be easier to remember; something like get_control=True that toggles the requested suffix. Any thoughts?

[karlwx]

Sure, those are great ideas. I agree that get_control=True might be easier to remember since the product suffix isn't very descriptive. I can make that change and update the docs notebook!

[blaylockbk]

Thanks @karlwx and @williamhobbs!