Add function to remove environments tracked by ggplot2

[vandenman]

@JorisGoosen this is an alternative/ global approach for https://github.com/jasp-stats/INTERNAL-jasp/issues/1755

Two things to consider:

1. Implementing this globally might be tricky because it can definitely break existing plot code (see demoBad in inst/examples/ex-removeEnvironments.R). I'd argue that all code that breaks because of this is poorly written (and needs a rewrite).
2. It's not super fast (yet). Right now, it recurses very deeply in ggplot2 structures. We can probably exit early and speed this up, but I haven't tested that yet. It's probably better to first check if this doesn't break too many figures in JASP.

To quickly test this in JASP you can change this line
https://github.com/jasp-stats/jaspResults/blob/49dcd41be799272b69ee562e496ee57afaaf33fa/R/zzzWrappers.R#L509
into

		plotObject  = function(x) if (missing(x)) private$jaspObject$plotObject   else private$jaspObject$plotObject   <- removeEnvironments(x),

and just dump the contents of R/removeEnvironments.R at the bottom of the file. Ugly, but otherwise you need to ensure that modules actually call the right jaspGraphs and all that...

[vandenman]

Now that I think of it, this part (and the other parts that remove environments) actually remove all environments. Perhaps I should add an option to only remove specified environments (by default ggplotObj$plot_env).