Standarize w/ separate package all eliminationOrdering methods

[dehann]

see new package https://github.com/JuliaRobotics/VariableEliminationOrderings.jl

Background

• https://www.coursera.org/lecture/probabilistic-graphical-models-2-inference/finding-elimination-orderings-ckOIz
• Local Caesar.jl Wiki page of known references
• Papers and thesis Caesar literature page
• https://en.wikipedia.org/wiki/Variable_elimination

Existing Usage in IncrementalInference

https://github.com/JuliaRobotics/IncrementalInference.jl/blob/870e518fc7e808b911bcd50682a2f786a793a80b/src/FactorGraph.jl#L1138-L1167

And the new RCS package to be included: https://discourse.julialang.org/t/implementing-cuthill-mckee/9268/31

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Also see discussion at (pending license):

• JuliaSmoothOptimizers/AMD.jl#36

One solution might be to have JuliaRobotics/VariableEliminationOrderings.jl provides a mechanism to include more methods depending on the desired license restrictions.