Support derivative boundary conditions

[ErikQQY]

Fix: #281
Fix: #83
Could possibly unblock #282

with this PR, we can just specify the derivative boundary condition as

function bc!(res, u, p, t)
    res[1] = u(0.0)[1] + pi / 2
    res[2] = u(1.0, Val{1})[2] - pi / 2 # u(1.0, Val{1})[2] is the u2'(1.0)=pi/2
end

[github-actions]

Benchmark Results

	master	9736263...	master / 9736263...
Simple Pendulum/IIP/BoundaryValueDiffEqMIRK.MIRK2()	1.14 ± 0.027 s	1.15 ± 0.043 s	0.991 ± 0.044
Simple Pendulum/IIP/BoundaryValueDiffEqMIRK.MIRK3()	16 ± 0.62 ms	16.2 ± 1.3 ms	0.986 ± 0.089
Simple Pendulum/IIP/BoundaryValueDiffEqMIRK.MIRK4()	3.01 ± 0.2 ms	3.01 ± 0.21 ms	1 ± 0.097
Simple Pendulum/IIP/BoundaryValueDiffEqMIRK.MIRK5()	8.78 ± 0.75 ms	8.79 ± 0.84 ms	0.998 ± 0.13
Simple Pendulum/IIP/BoundaryValueDiffEqMIRK.MIRK6()	1.55 ± 0.23 ms	1.54 ± 0.29 ms	1.01 ± 0.24
Simple Pendulum/IIP/MultipleShooting(10, Tsit5; grid_coarsening = false)	1.86 ± 0.66 ms	1.85 ± 0.62 ms	1.01 ± 0.49
Simple Pendulum/IIP/MultipleShooting(10, Tsit5; grid_coarsening = true)	3.15 ± 1 ms	3.12 ± 0.95 ms	1.01 ± 0.44
Simple Pendulum/IIP/MultipleShooting(100, Tsit5; grid_coarsening = false)	0.0666 ± 0.02 s	0.063 ± 0.0096 s	1.06 ± 0.36
Simple Pendulum/IIP/MultipleShooting(100, Tsit5; grid_coarsening = true)	0.0788 ± 0.021 s	0.0786 ± 0.022 s	1 ± 0.4
Simple Pendulum/IIP/Shooting(Tsit5())	0.248 ± 0.075 ms	0.246 ± 0.07 ms	1.01 ± 0.42
Simple Pendulum/OOP/BoundaryValueDiffEqMIRK.MIRK2()	1.3 ± 0.012 s	1.31 ± 0.021 s	0.994 ± 0.019
Simple Pendulum/OOP/BoundaryValueDiffEqMIRK.MIRK3()	19 ± 5.8 ms	19 ± 6 ms	1 ± 0.44
Simple Pendulum/OOP/BoundaryValueDiffEqMIRK.MIRK4()	3.51 ± 0.17 ms	3.49 ± 0.16 ms	1.01 ± 0.067
Simple Pendulum/OOP/BoundaryValueDiffEqMIRK.MIRK5()	10.2 ± 0.66 ms	10.2 ± 0.59 ms	1 ± 0.087
Simple Pendulum/OOP/BoundaryValueDiffEqMIRK.MIRK6()	1.79 ± 0.16 ms	1.81 ± 0.15 ms	0.99 ± 0.12
Simple Pendulum/OOP/MultipleShooting(10, Tsit5; grid_coarsening = false)	3.51 ± 2.8 ms	3.51 ± 2.9 ms	1 ± 1.2
Simple Pendulum/OOP/MultipleShooting(10, Tsit5; grid_coarsening = true)	5.98 ± 4.9 ms	5.99 ± 4.8 ms	0.999 ± 1.1
Simple Pendulum/OOP/MultipleShooting(100, Tsit5; grid_coarsening = false)	0.115 ± 0.018 s	0.114 ± 0.02 s	1.01 ± 0.24
Simple Pendulum/OOP/MultipleShooting(100, Tsit5; grid_coarsening = true)	0.141 ± 0.025 s	0.14 ± 0.025 s	1.01 ± 0.25
Simple Pendulum/OOP/Shooting(Tsit5())	0.634 ± 0.053 ms	0.633 ± 0.078 ms	1 ± 0.15
time_to_load	5 ± 0.035 s	5 ± 0.0078 s	1 ± 0.0072

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).