Reduce memory footprint

[aimxhaisse]

On Holesky, the watcher takes about 8GiB of ram to be able to watch the entire network, as the entire data set is a few hundreds MiB, there may be way to reduce the footprint by trying to explicitly delete a bunch of dicts/sets after use.

[nalepae]

I guess this could help.
With the GET endpoint, it was more convenient to retrieve all validators instead of a (potentially very big) subset.
==> Big memory footprint, especially on Holesky.

With the POST endpoint, it will be simpler to retrieve a subset of validators.

[nalepae]

https://ethereum.github.io/beacon-APIs/?urls.primaryName=dev#/Beacon/postStateValidators