Improve vectorization of kernels

[chhwang]

Affected operators: reduce_*, softmax, scale, exp, sqrt, rsqrt, rope, relu, gelu, sigmoid, add, sub, mul, div, cast

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (0fb0a3e) 83.72% compared to head (98289a3) 83.48%.

Files	Patch %	Lines
ark/ops/ops_reduce.cc	33.33%	4 Missing ⚠️
ark/ops/ops_arithmetic.cc	98.57%	1 Missing ⚠️
ark/ops/ops_math.cc	98.66%	1 Missing ⚠️
ark/ops/ops_test_common.cc	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #189      +/-   ##
==========================================
- Coverage   83.72%   83.48%   -0.25%     
==========================================
  Files          96       87       -9     
  Lines        6373     6126     -247     
==========================================
- Hits         5336     5114     -222     
+ Misses       1037     1012      -25     

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