[static runtime] add static registry (#48258)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48258
This will enable closed source contributions
Test Plan: buck test mode/no-gpu //caffe2/benchmarks/static_runtime:static_runtime_cpptest
Reviewed By: hlu1
Differential Revision: D25031586
fbshipit-source-id: def859fa2fb4f01910b040242662a51b85804f01
