feature request: collect and deduplicate guides in plot composition

[ilia-kats]

When composing multiple plots in a grid, it would be really useful to be able to remove guides from individual plots and instead show a global guide for the the entire composition, similar to what R's patchwork does with plot_layout(guides="collect").

[has2k1]

This is certainly in the works. If it does not make it to 0.16.0 it will in the one after.