Use shift values for FloorPlot

[Mael-Le-Garrec]

Currently, the FoorPlot uses the position of the elements to plot them but does not use the shift_x, shift_y and rotation variables like rot_s_rad.

To be probably implemented around here: https://github.com/xsuite/xplt/blob/main/xplt/line.py#L418

I made a basic change that should work for thick elements, but only works when a line element is provided, as the survey only does not seem to contain the shift information (only ref_shift, set to 0).

Mael-Le-Garrec@a2f4b21

[eltos]

Thank you @Mael-Le-Garrec for this. Since you already started implementing it, would you like to submit a PR? I think the projection handling might need some fine-tuning to work for all the cases, but other than that it looks pretty good already.

[Mael-Le-Garrec]

I'm definitely not sure I'm covering all the cases but I can do a PR with that code already sure!