Merge the sharp edge tagging into bm_mesh_loops_calc_normals,
this has the advantage that edge tagging can be performed as part of
walking over each vertices edges - instead of tagging in a separate loop.
Even though this will tag edges twice (once for each vertex),
the computation isn't heavy as it's only calculating a dot-product
between the two face users to compare the angle.
This change combined with 4ba06ad0a8
makes BM_loops_calc_normal_vcos around 5.68x faster,
with an overall speedup over 2.6x when transforming a high poly mesh.
(tested on a system with 32 cores).
Reviewed By: mont29
Ref D11970
39b2a7bb7e