Add unit tests for TBE API v1 compatibility (#4926)

Summary:
Pull Request resolved: #4926

X-link: facebookresearch/FBGEMM#1950

TBE changed its interface to be a unified API (TBE API V2). This changes the frontend (i.e., `split_embedding_codegen_lookup_{optimizer}_function_pt2) and backend pipeline. See the changes in the diagram below. V1 API is greyed out and V2 API are marked with **. The backend CPU and CUDA host functions and kernels remain the same.

 {F1982217763}

Some production models/packages (e.g., lex_ig_o3_package) still use the old frontend API (v1) with new backends. Hence, we need to ensure the support for v1 API and pipeline against any updates in backend CPU and CUDA host functions and kernels.

This diff adds unit tests to testTBE API v1 compatibility. These tests will invoke `split_embedding_codegen_lookup_{optimizer}_function_cpu` or `split_embedding_codegen_lookup_{optimizer}_function`, and follow through v1 pipeline. These tests would have caught failures found in S566486.

Reviewed By: gchalump, ionuthristodorescu, q10

Differential Revision: D83020965

fbshipit-source-id: 5238ea02e0d68376d1de2434e5b146620eb6887a

Author: spcyppt