Add sub operator for Arm backend (#4074)

Summary:
Implemented node visitor, quantizer, and test.
TOSA MI and BI passes, U55 BI fails (expectedly) on Vela compilation.

Refactored code shared between sub and add.

Change-Id: Ifc9fc4ae083f3ed868ad763e4301e5fe87468a25

Pull Request resolved: https://github.com/pytorch/executorch/pull/4074

Reviewed By: mergennachin

Differential Revision: D59259308

Pulled By: digantdesai

fbshipit-source-id: ce10e9b1a583e6374e5f1c5815dc11c0d0e7aa5b