[D23047144 Duplicate][2/3][lite interpreter] add metadata when saving and loading models for mobile (#43584)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43584
1. add `metadata.pkl` to `.bc` file which includes the model info that we are interested in
2. load `metadata.pkl` as a attribute `unordered_map<string, string>` in the module
ghstack-source-id: 110730013
Test Plan:
- CI
```buck build //xplat/caffe2:jit_module_saving
```
```buck build //xplat/caffe2:torch_mobile_core
```
Reviewed By: xcheng16
Differential Revision: D23330080
fbshipit-source-id: 5d65bd730b4b566730930d3754fa1bf16aa3957e
