Performance: Thread Management

[bw-solana]

There is a ton of work to do to wrangle all of the threads in Agave. This potentially includes things like:

1. Reducing overall number of threads (threads exceed cores by an order of magnitude) by combining some services, shrinking thread pools, not scaling thread pools to num CPUs in many cases.
2. There are several places in the code where we have rayon thread pools to parallelize work, but the average amount of work to complete is very small. The overhead of farming out to rayon pool is significant. We would be better off just using the current thread when the amount of work is small.

Steve has put together a thread related project here: https://github.com/orgs/anza-xyz/projects/3

• window_service: use the service thread as a rayon worker thread #3876