Move mobile specific CPUCachingAllocator to c10/mobile folder. (#45364)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45364
Plus add some more comments about the usage, limitations and cons.
Test Plan: Build and run benchmark binary.
Reviewed By: gchanan
Differential Revision: D23944193
fbshipit-source-id: 30d4f4991d2185a0ab768d94c846d73730fc0835
