Add docs and warning in logs to disable SWAP

When swap memory is enabled the execution speed may decrease from 300Mgas/s to 10Mgas/s which is a significant bottleneck.

Documentation should warn uses to disable swap memory before running Erigon3.

Also, the guide to limit memory usage should be added

Optimal memory usage configuration for ~10GB

```
environment:
- GOGC=50
- GOMEMLIMIT=10GiB
command: |
--batchSize="120M"
```

Note that garbage collector will rip your CPU in order to reduce RAM usage, but it is very optimal if you want your erigon node to use less RAM so that you could run nodes for multiple networks with maximum execution performance.