Add planar layout to rustworkx

[enavarro51]

This draft PR adds the planar layout to the graph layout methods. This code incorporates and modifies the code from the open PR #475 for the Left/Right Planarity Test. It then creates the embedding that is ultimately converted to position coordinates for displaying the graph layout.

It follows the algorithms from Ulrik Brandes: The Left-Right Planarity Test 2009 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.217.9208
and M. Chrobak and T.H. Payne: A Linear-time Algorithm for Drawing a Planar Graph on a Grid 1989 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.51.6677
as well as the python code used in the networkx version of planar layout.

Remaining items include

• Additional error checking
• Docs
• More tests

[coveralls]

Pull Request Test Coverage Report for Build 2749795804

• 1 of 1082 (0.09%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-7.6%) to 89.516%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/layout/mod.rs	0	8	0.0%
src/layout/planar.rs	0	44	0.0%
retworkx-core/src/planar/lr_planar.rs	0	445	0.0%
src/layout/embedding.rs	0	584	0.0%

Totals
Change from base Build 2691937771:	-7.6%
Covered Lines:	12364
Relevant Lines:	13812

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 2905132284

• 750 of 1103 (68.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-2.3%) to 94.805%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/layout/planar.rs	38	44	86.36%
src/layout/embedding.rs	481	581	82.79%
rustworkx-core/src/planar/lr_planar.rs	220	467	47.11%

Totals
Change from base Build 2905042897:	-2.3%
Covered Lines:	13248
Relevant Lines:	13974

---

💛 - Coveralls

[georgios-ts]

Is Option the correct type here? These values will never be None. Creating an instance holding a None and later updating the weights with the correct values is redundant: store the final values right from the beginning!