Add loop inside sparse infill of lower layer
to provide archor for internal bridge.
This option controls how many lower layers generate
loop path.
Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: Ifdb6db9090115732aa2cacf5d155b587a10e18fc
(cherry picked from commit 4fdb87ecd5c2e680f6bad2d018ba39cd05f787ce)