[ExecuTorch] Add broadcast support for optimized add op (#8205)

* [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:

[ghstack-poisoned]

* [ExecuTorch] Add broadcast support for optimized add op

Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

[ghstack-poisoned]

* Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

[ghstack-poisoned]

* Update base for Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

[ghstack-poisoned]

* Update base for Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

[ghstack-poisoned]

* Update base for Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

[ghstack-poisoned]

* Update base for Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

Differential Revision: [D69491814](https://our.internmc.facebook.com/intern/diff/D69491814)

[ghstack-poisoned]

* Update base for Update on "[ExecuTorch] Add broadcast support for optimized add op"


Summary:
This brings add op to feature parity, wrt, broadcasting, to mul op in
optimized kernels lib

Test Plan:
tests added

Reviewers:

Subscribers:

Tasks:

Tags:

cc larryliu0820 manuelcandales

Differential Revision: [D69491814](https://our.internmc.facebook.com/intern/diff/D69491814)

[ghstack-poisoned]