`updateAndGet` could actually call the internal method more than once on contention.
If I read the JavaDocs, it says:
```* @param updateFunction a side-effect-free function```
So, it could be getting multiple updates on contention, thus having a race condition where stats are double counted.

To fix, I am going to use a `ReadWriteLock`. The `LongAdder` objects allows fast thread safe writes in high contention environments. These can be protected by the `ReadWriteLock::readLock`.

When stats are persisted, I need to call reset on all these adders. This is NOT thread safe if additions are taking place concurrently. So, I am going to protect with `ReadWriteLock::writeLock`.

This should prevent race conditions while allowing high (ish) throughput in the highly contention paths in inference.

I did some simple throughput tests and this change is not significantly slower and is simpler to grok (IMO).

closes  elastic#54786