Add DEStats and more docstrings for BVPM2

[ErikQQY]

Checklist

• [x] Appropriate tests were added
• [x] Any code changes were done in a way that does not break public API
• [x] All documentation related to code changes were updated
• [x] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [x] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[github-actions[bot]]

Benchmark Results

	master	fb8239baac649d...	t[master]/t[fb8239baac649d...]
Simple Pendulum/IIP/MultipleShooting(10, Tsit5; grid_coarsening = false)	1.35 ± 0.056 ms	1.35 ± 0.048 ms	1
Simple Pendulum/IIP/MultipleShooting(10, Tsit5; grid_coarsening = true)	2.62 ± 0.094 ms	2.6 ± 0.078 ms	1.01
Simple Pendulum/IIP/MultipleShooting(100, Tsit5; grid_coarsening = false)	29.9 ± 3.7 ms	29.6 ± 3.6 ms	1.01
Simple Pendulum/IIP/MultipleShooting(100, Tsit5; grid_coarsening = true)	1.07 ± 0.0075 s	1.07 ± 0.012 s	1.01
Simple Pendulum/IIP/Shooting(Tsit5())	0.177 ± 0.0057 ms	0.18 ± 0.0041 ms	0.988
Simple Pendulum/OOP/MultipleShooting(10, Tsit5; grid_coarsening = false)	3.22 ± 0.21 ms	3.17 ± 0.17 ms	1.02
Simple Pendulum/OOP/MultipleShooting(10, Tsit5; grid_coarsening = true)	5.86 ± 5.1 ms	5.8 ± 4.8 ms	1.01
Simple Pendulum/OOP/MultipleShooting(100, Tsit5; grid_coarsening = false)	0.0847 ± 0.0046 s	0.0839 ± 0.0029 s	1.01
Simple Pendulum/OOP/MultipleShooting(100, Tsit5; grid_coarsening = true)	4.58 ± 0.025 s	4.5 ± 0.013 s	1.02
Simple Pendulum/OOP/Shooting(Tsit5())	0.705 ± 0.038 ms	0.698 ± 0.035 ms	1.01
time_to_load	8.26 ± 0.024 s	8.28 ± 0.0099 s	0.997

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR. Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).