Fast nodes

[liamhuber]

Introduces two new node classes following our discussion here:

• FastNode: a Node that has default values for all input and is hard-coded to update automatically and at instantiation
• SingleValueNode: a FastNode that has exactly one output channel. Attribute and item access falls back to looking at this output value.

This gives some quality of life improvements for working with these really simple nodes in the notebook. E.g. we can now do the following and get a sensible result:

from pyiron_contrib.workflow.nodes import bulk_structure
struct = bulk_structure()
type(struct)
>>> abc.BulkStructure
struct.plot3d()
# Falls back to looking at the output structure to find the method, 
# and successfully returns the NGLWidget

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[coveralls]

Pull Request Test Coverage Report for Build 4854021870

• 37 of 50 (74.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 12.735%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyiron_contrib/workflow/node.py	34	39	87.18%
pyiron_contrib/workflow/nodes.py	0	8	0.0%

Files with Coverage Reduction	New Missed Lines	%
pyiron_contrib/workflow/nodes.py	1	0%

Totals
Change from base Build 4853782170:	0.2%
Covered Lines:	1561
Relevant Lines:	12258

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