Workflow: Better io

[liamhuber]

This is docs and type hints except that now the key under which a channel is stored in an IO collection doesn't need to be that channel's label.

The rationale for this is that workflows should dynamically be creating IO collections with keys like f"{node.label}_{channel.label}", but I don't want them to be altering the underlying channel label. Right now Workflow does this by just making a (dot)dict out of the channel objects, but it would be nice to use the formal IO class for the collection so we get access to its helper methods and can have consistent typing between Workflow and Node for what inputs and outputs look like.

@samwaseda, because this is almost just doc changes, and I want the functional change for us in #729, I'll probably merge it without review. But if you want to take a peek anyhow and leave some comments where anything is unclear/poorly worded, I would be happy to open a patching PR to polish it up.

[github-actions]

👈 Launch a binder notebook on branch pyiron/pyiron_contrib/better_io

[github-actions]

Pull Request Test Coverage Report for Build 5350236287

• 33 of 33 (100.0%) changed or added relevant lines in 2 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 11.887%

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Files with Coverage Reduction	New Missed Lines	%
pyiron_contrib/workflow/channels.py	2	89.1%

Totals
Change from base Build 5347569066:	0.0%
Covered Lines:	1671
Relevant Lines:	14057

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💛 - Coveralls