[minor] Semantics

[liamhuber]

Breaking out responsibility for the label, parent/child relationships (including semantic uniqueness), path, root, etc. into separate classes. Long term, this is also useful for non-workflow/non-node semantic objects used to indicate non-data connections between workflows.

Part of #243

Only user-facing changes are that Composite.nodes got renamed to Composite.children and is a bidict instead of DotDict.

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:point_left: Launch a binder notebook on branch _pyiron/pyironworkflow/semantics

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Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
:white_check_mark: +0.20% (target: -1.00%)	:white_check_mark: 94.84%

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (9d7b286298f0eeaea77e34f3a86ad42aa004db8d) | 3151 | 2734 | 86.77% | | | Head commit (72827593acfbee95736bc4692dbf4f34ec8c890d) | 3231 (+80) | 2810 (+76) | 86.97% (**+0.20%**) | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#244) | 213 | 202 | **94.84%** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

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[coveralls]

Pull Request Test Coverage Report for Build 8333157217

Details

• 225 of 237 (94.94%) changed or added relevant lines in 8 files are covered.
• 72 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.03%) to 91.766%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyiron_workflow/semantics.py	171	183	93.44%
<!--	Total:	225	237	94.94%	-->

Files with Coverage Reduction	New Missed Lines	%
meta.py	1	98.21%
macro.py	9	89.33%
workflow.py	13	79.78%
composite.py	22	90.3%
node.py	27	92.2%
<!--	Total:	72		-->

Totals
Change from base Build 8256110010:	-0.03%
Covered Lines:	5996
Relevant Lines:	6534

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💛 - Coveralls

[liamhuber]

Test failures were a timeout downloading from conda, I guess this is 100% on the GitHub side and will just re-run.

[liamhuber]

Faulty re-run button may be a browser version problem on my end; it worked fine in firefox