Enable loading int8 prepacked models in PredictorContainer
Summary: To test the int8 ads models on CPU and accelerators with the ads replayer, we need to load the PREPACKING_INIT_NET_TYPE in the int8 model to initialize the int8 w_packed blobs.
Test Plan:
Ads replayer test.
P74811059
Reviewed By: zrphercule
Differential Revision: D16518888
fbshipit-source-id: cee212710ad37d9e491c970b25b2fe484373e5e4