layout: end connections at outside labels

[gavin-ts]

Summary

End connections at outside labels regardless if it is a container.
Previously we would stop dagre connections at outside container labels, but this wouldn't account for other scenarios such as the person shape having an outside bottom label position as a non-container.

Details

• fixes second issue in low-opacity label masking on shape labels #892
• trace both Src and Dst ends of connections to any outside label

before/after

e2ereport