In-house processing of marginaleffects objects

[DominiqueMakowski]

Currently we call the tidy() function,

parameters/R/methods_marginaleffects.R

Lines 12 to 15 in 804cfcb

	out <- insight::standardize_names(
	marginaleffects::tidy(model, conf_level = ci, ...),
	style = "easystats"
	)

which is defined here: https://github.com/vincentarelbundock/marginaleffects/blob/a6730a3560dbf4220d4bf82da141400fa235b996/sandbox/tidy_old.R#L92

But this strongly limits our capabilities (especially in Bayesian cases). We should probably not rely on tidy and reimplement it using bayestestR for the processing of draws.

easystats/modelbased#302

[strengejacke]

We should probably submit bayestestR (easystats/bayestestR#691) the next days, then we should have the basis for this PR.