Leaky relu in metal shader (#78544)
Summary:
Heavily referenced how Hardswish was implemented.
This is a great intro task to get a taste of how a torch method is implemented in shader and tested.
Test Plan:
Compared in metal shader metal version and cpu version result in tests.
https://pxl.cl/251kT
Reviewed By: SS-JIA
Differential Revision: D36732187
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78544
Approved by: https://github.com/SS-JIA
