More flexible plot recipe

[nathanaelbosch]

Now that WorkPrecision contains not just a single error and runtimes, but also solver stats like the number of function evaluations, discrete step sizes for non-adaptive solvers, and a range of computed errors, we should provide some convenient functionality to plot these.

Example use-cases I see are

• Specifying which error to plot against runtime (currently it plots the one saved in wp.error_estimate, but it could be l2, final, ...)
• Plotting error against dts for fixed-step solvers (currently possible with view=:dt_convergence; maybe a more general API would simplify the code?)
• Plotting error against stats.nf (as already requested back in 2020 in feval vs error plot #64)
• Plotting one error against another one (particularly relevant for the probabilistic solvers in ProbNumDiffEq.jl as to evaluate calibration we plot a calibration metric agains an error)
• Plotting tolerances against error

How should the API look?

I'm not quite sure about this, but maybe simple x::Symbol and y::Symbol keyword arguments would be enough?
Something along the lines of

@recipe function f(
    wp_set::WorkPrecisionSet;
    x::Symbol = wp_set.error_estimate,
    y::Symbol = :times,
    view = :benchmark,
    color = nothing
    )

and then the x and y data would get filled with the corresponding values.

What do you think, would this make sense? I will try to see if I can get a minimal example working soon., and open a corresponding draft PR.