feat: add persistent term to state retrieving benchmark

[polvalente]

I noticed that there was a benchmark about state retrieval which did not include persistent_terms. I added them to the benchmark. However, there is no benchmark for writing speed or for read-write roundtrip speed. Maybe we should add them in a next pull request?

[devonestes]

Good idea! There's just a merge conflict, but after that's fixed I think this is a good addition.

[polvalente]

Good idea! There's just a merge conflict, but after that's fixed I think this is a good addition.

@devonestes conflicts resolved! I guess most of them were due to some auto-formatter in my editor