## Problem
There was a bug in dynamic rate limiter, which exhausted CPU in proxy
and proxy wasn't able to accept any connections.
## Summary of changes
1. `if self.available > 1` -> `if self.available >= 1`
2. remove `timeout_at` to use just timeout
3. remove potential infinite loops which can exhaust CPUs.
## Problem
Computes that are healthy can manage many connection attempts at a time.
Unhealthy computes cannot. We initially handled this with a fixed
concurrency limit, but it seems this inhibits pgbench.
## Summary of changes
Support AIMD for connect_to_compute lock to allow varying the
concurrency limit based on compute health
## Problem
There is an unused dead code.
## Summary of changes
Let's remove it. In case we would need it in the future, we can always
return it back.
Also removed cli arguments. They shouldn't be used by anyone but us.
