Add pattern to merge consecutive splits (#100107)
Summary:
Fx pass for "split->split => split" pattern
{F959486105}
Test Plan:
* CI tests
* Run in a notebook on CMF MIMO
{F959938752}
Differential Revision: D45204109
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100107
Approved by: https://github.com/jansel
