Implement Khan and Reversed DFS Post Order algorithms

[FiasKr]

This pull request introduces two new algorithms for traversing the inheritance graph: Khan's algorithm and a reversed DFS post-order traversal. Both are topological sort algorithms that can be used to determine the order of inheritance (#3361).

Changes

common/src/main/java/me/lucko/luckperms/common/graph/TraversalAlgorithm.java

• Added REVERSED_DFS_POST to the TraversalAlgorithm enum. This algorithm provides a topological sort by reversing the result of a depth-first post-order traversal.
• Added KHAN to the TraversalAlgorithm enum. This is an implementation of Khan's algorithm for topological sorting.

common/src/test/java/me/lucko/luckperms/common/model/InheritanceTest.java

• Added REVERSED_DFS_POST and KHAN to the parameterized test testInheritanceTree.
• Added a new standalone test testKhanAlgorithm to specifically test the Khan's algorithm implementation.
• Added a new standalone test testReversedDfsPostAlgorithm to specifically test the reversed DFS post-order algorithm.

[lucko]

Do you have a use for this? Can you give an example (in context) where this is useful in LuckPerms with groups?

[FiasKr]

Do you have a use for this? Can you give an example (in context) where this is useful in LuckPerms with groups?

I was just trying to resolve this fairly old issue: #3361
If it is no longer needed, feel free to close PR and Issue :)