1. Previously if there are multiple sharp tails in a layer, some will be
missed. To fix this, we should not skip if the current layer is already
detected as sharp tails.
2. Do not mistakenly detect sharp horns as sharp tails by only detecting
the overhang areas larger than half of the extrusion line width.
Github: #1578
Jira: STUDIO-2659
Change-Id: If7ba5c9ae547d3051551aa6fa34eb6214d01a46d