Add utils to inspect fp16/int8 packed weights (#32979)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32979
Since we use prepacked weights in the Fp16 FCs and future Int8 FCs in production Ads models, we provide the python utils to inspect the unpacked format of the weights for debugging purpose. The main interfaces are the following:
```
from deeplearning.numeric_suite.toolkit import packed_weights_inspector
# inspect fp16 packed weights
unpacked_fp16_weights = packed_weights_inspector.extract_fp16_fc_packed_weights(fp16_weight_blob_name)
# inspect int8 packed weights
unpacked_int8_weights, qparams = packed_weights_inspector.extract_int8_fc_packed_weights(int8_weight_blob_name)
```
Test Plan:
```
buck test mode/opt deeplearning/numeric_suite/toolkit/test:packed_weights_inspector_test
```
Reviewed By: amylittleyang
Differential Revision: D19724474
fbshipit-source-id: e937672b3722e61bc44c2587aab2288a86aece9a
