Fix EPLB + NVFP4: exclude broadcast scales and fix stale quant config
Cherry-pick of PR #34646 (elvircrn/fix-eplb-nvfp4-contiguous).
Pre-compute g1/g2 alphas as registered parameters so EPLB rearranges
them alongside expert weights. Without this, the quant config caches
g1_alphas = a_scale * w_scale_2 once at init, and EPLB's in-place
rearrangement of w_scale_2 leaves the cached product stale.
Also excludes broadcast activation scales (w13_input_scale,
w2_input_scale) from EPLB to prevent contiguity assertion crash
(these are expanded stride-0 tensors from .max().expand()).
Co-Authored-By: Elvir Crncevic <elvircrn@users.noreply.github.com>
Signed-off-by: Tyler Michael Smith <tlrmchlsmth@gmail.com>