build: Inline GsLozengeLayout into gs-lozenge.c
This follows the pattern of the other descendants of the GsLayoutManager to inline the layout into the source where it's used, without providing unneeded overhead with a code not being used at all/anywhere else.
Not a bad statistic:
4 files changed, 57 insertions(+), 210 deletions(-)
The idea comes from here: !1340 (comment 1457823)