Add immediate_dominators function

[airwoodix]

If I didn't miss it, dominance-related functionality is not yet exposed. Apologies if I missed it.

This patch adds a rustworkx.immediate_dominators function that has the same functionality as networkx.immediate_dominators. The core functionality is directly provided by the petgraph crate, such that only a thin Python binding was necessary.

The tests are directly ported from those in networkx.

An equivalent to networkx.dominance_frontiers could be added in a later patch.

[IvanIsCoding]

Thanks for submitting this! It is a welcome addition.

I just left some minor comments but overall this is very close to getting merged and released in 0.16

Note: and Clippy has some gotchas too but those should be easy to fix. Run cargo clippy or look at the CI failure for the lint output

[airwoodix]

Thanks for the review!

I addressed the comments and rebased the branch.

Following the new function's renaming, I edited the PR title and description.

[coveralls]

Pull Request Test Coverage Report for Build 11928735689

Details

• 26 of 26 (100.0%) changed or added relevant lines in 2 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.005%) to 95.863%

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Files with Coverage Reduction	New Missed Lines	%
rustworkx-core/src/generators/random_graph.rs	2	85.04%

Totals
Change from base Build 11923243578:	-0.005%
Covered Lines:	18259
Relevant Lines:	19047

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💛 - Coveralls

[IvanIsCoding]

Fantastic. This should come out when 0.16 is released 🚀