Update base for Update on "[Executorch] Refactor op_mul's broadcasting utils"

Summary:
Refactoring broadcast handling utils that were added for op_mul. This is
in prepartion use these utils to handle broadcast for other ops such as
add, sub, div.
Plus remove a redundant test

Test Plan:
optimized_kernels_test in CI

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

[ghstack-poisoned]

Author: kimishpatel