Closed regions search refactoring

[srudenkoamc]

BACKGROUND:

• Network.FindAllClosedRegions cannot find all closed regions correctly in some cases.

DESCRIPTION:

• Moved the logic that searches for closed regions from Network.FindAllClosedRegions into a separate class NetworkCycleCoverage.
• Added NetworkNode class that contains both index and position of vertex. It allows to simplify the code significantly.
• Added NetworkEdge class that is similar to LocalEdge class, but is based on NetworkNode and has several additional methods.
• Replaced _adjacencyList with an adjacency matrix based on NetworkNode and NetworkEdge.
• Algorithm stays the same. The tests are not affected by the changes.

TESTING:

• The tests are not affected by the changes.
• Additionally tested on https://hypar.io/workflows/820ea7b7-1bf1-4779-9a6b-20da7dd6c969.

FUTURE WORK:

• Remove leaf branches before search.
• Should be a good idea to traverse edges instead of nodes.

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This change is 

[srudenkoamc]

One little comment.

Reviewed 5 of 5 files at r1, all commit messages. _Reviewable_ status: 1 change requests, 0 of 1 approvals obtained (waiting on @srudenkoamc)

_Elements/src/Search/NetworkCycleCoverage.cs line 192 at r1 (raw file):_

                var edge = GetEdge(path[j], path[j + 1]);

                // if (edge == null)

Let's remove this commented code. Even though it was there previously, I don't think it should be.

@wynged , fixed in https://github.com/hypar-io/Elements/pull/992/commits/399ec29cbb7bded43592a0e552f7bc6c9818f9eb.