Implement unlift_and_swap function

[angelayi]

Summary: Implement a new swapping API which does the following:

1. Takes an exported program and torchrec serializer
2. Constructs torchrec modules based on serialized metadata stored in the exported program
3. Unlifts the exported program to a normal nn.Module
4. Partitions out nodes and swaps them out with calls to the torchrec modules

Differential Revision: D63683421