Add one or more energy conservation benchmarks

[nathanaelbosch]

Something similar to these SciML Benchmarks would be nice to have:

• Henon-Heiles Energy Conservation: https://docs.sciml.ai/SciMLBenchmarksOutput/stable/DynamicalODE/Henon-Heiles_energy_conservation_benchmark/
• Quadruple Boson Energy Conservation: https://docs.sciml.ai/SciMLBenchmarksOutput/stable/DynamicalODE/Quadrupole_boson_Hamiltonian_energy_conservation_benchmark/#Quadruple-Boson-Energy-Conservation
• Single Pendulum Comparison (currently broken): https://docs.sciml.ai/SciMLBenchmarksOutput/stable/DynamicalODE/single_pendulums/#Solving-single-pendulums-by-DifferentialEquations.jl

This part of the ProbNumDiffEq.jl documentation shows how we can do energy conservation, and that's what we'd want to evaluate and compare to projection methods and symplectic methods.