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 D11928 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).

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This must be applied on top of D11928.