adjust connections and labels for shapes with 3d or multiple

[gavin-ts]

Summary

Updates dagre and elk layouts to adjust connections and labels for shapes with 3d or multiple.

Details

• fixes layout=dagre: container labels are too close to the top edge of "multiple" style containers #1339
• fixes Pushback arrowheads when multiple is set #63
• adds multiple_offset multiple_offset_left tests
• fixes 3d hexagon offset calculations
• fixes some floating point issues causing differences between CI and local

multiple_offset before

multiple_offset after

multiple_offset_left before/after

e2ereport

[alixander]

while ur doing this, how hard would it be to add on adjusting for stroke width? if nontrivial, make another issue plz

[gavin-ts]

while ur doing this, how hard would it be to add on adjusting for stroke width? if nontrivial, make another issue plz

created #1347 for this. haven't yet figured out why that is slightly off there, but stroke width should already be accounted for in the arrowhead adjustments