[SR] Factor operator() implementation into separate function (#67125)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67125
Using explicit template instantiations in D31659973 (https://github.com/pytorch/pytorch/commit/f2582a59d0835323ebf143726ea79ba52e7cceff) was a bad idea. The problem is that the lvalue instantiation was for a `const` vector of `IValue`, meaning that if you tried to pass SR a non-const vector of arguments, the linker would fail to find the symbol.
The reason we didn't catch this in D31659973 (https://github.com/pytorch/pytorch/commit/f2582a59d0835323ebf143726ea79ba52e7cceff) was because predictor always passes a `const` reference anyways. But we should fix this to prevent unexpected problems in the future.
Test Plan: `buck test caffe2/benchmarks/static_runtime/...`
Reviewed By: hlu1
Differential Revision: D31873406
fbshipit-source-id: 5ab5a03334bed925cec11facadcedf9bec9b90ad
