Topological Sort

[drio18]

Here, we include new classes for performing a topological sort into misc_utils. I found myself of need of this for work in the cgap-portal repo, and we're using something similar in magma, so I figured I would pull this here for wider use.

As mentioned in comments, the source code was essentially copied from python's graphlib module which is only available in versions >=3.9. I added some simple tests to ensure high-level functionality but far from exhaustive given the source.

[coveralls]

Pull Request Test Coverage Report for Build 3831563546

• 94 of 108 (87.04%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 73.587%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dcicutils/misc_utils.py	94	108	87.04%
<!--	Total:	94	108	87.04%	-->

Totals
Change from base Build 3622858250:	0.2%
Covered Lines:	5898
Relevant Lines:	8015

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💛 - Coveralls