* add process slashings
* verify sig
* add method
* add test
* add in process slashings functionality
* target state for aggregate
* comment
* Radek comments
* Move domain function and all signing root functions from beacon-chain/core/helpers to beacon-chain/core
* @terencechain suggestion to put these methods under core/signing
* Bring in rest of the validator chagnes
* Go fmt
* Deepsource
Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>
Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>