* Refactor stats to use atomics
When we are dealing with a high number of connections, generated
stats cannot be consumed fast enough by the stats collector loop.
This makes the stats subsystem inconsistent and a log of
warning messages are thrown due to unregistered server/clients.
This change refactors the stats subsystem so it uses atomics:
- Now counters are handled using U64 atomics
- Event system is dropped and averages are calculated using a loop
every 15 seconds.
- Now, instead of snapshots being generated ever second we keep track of servers/clients
that have registered. Each pool/server/client has its own instance of the counter and
makes changes directly, instead of adding an event that gets processed later.
* Manually mplement Hash/Eq in `config::Address` ignoring stats
* Add tests for client connection counters
* Allow connecting to dockerized dev pgcat from the host
* stats: Decrease cl_idle when idle socket disconnects
