Make tracing in code gen optional (#33715)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33715
Tracing codes depend on the full JIT, which is not available in lite interpreter. Use `-c pt.disable_gen_tracing=1` to turn off generating tracing part.
ghstack-source-id: 99252322
Test Plan:
```
buck build xplat/caffe2:torch -c pt.disable_gen_tracing=1
```
The tracing part of generated/VariableType_?.cpp will not be generated.
Reviewed By: smessmer
Differential Revision: D19684577
fbshipit-source-id: a1e5b80eca5e51c7bf72b5cc8f0e36c2135fabc2
