refactor vector_index benchmark and add a index building benchmark

[chebbyChefNEQ]

Why

We don't have an e2e index building benchmark, which is helpful for understanding latency and profiling for bottlenecks in indexing building.

What changed

• extract create_file to lance::utils::testing
• extract out index building from create_file to create_vector_index
• add a new benchmark vector_index_build, where we bench mark the time required for building Ivf_PQ index