Benchmarking

[bhelx]

This is a general issue to implement benchmarking of the Extism runtime and tracking of benchmarks over time.
From my limited research, I think we could use cargo bench and this GH action https://github.com/benchmark-action/github-action-benchmark to track the data over time.

What we choose to track and which tools we use is up for debate.

Related to #420

[lukevp]

Would the benchmarks only be in rust natively? Or is there any planning around benchmarking all of the SDKs and PDKs too? It would be interesting to know the relative performance of each.