1. reduce the gap between blade-shape overhang and support
github: #3667
2. improve sharp tail detection of blade-shape overhangs by introducing
lslices_extrudable.
github: #2786, #3367
jira: STUDIO-5065, STUDIO-6038
Change-Id: I4e899eace1aa28b100a6f4ce2b8d740c317f5530
(cherry picked from commit 08328b848e39c345b6c7b64021d1e0f04df24d08)
(cherry picked from commit 22056d5f7e7bef5574b53fc0453781cd365bf0e1)