Cleanup extrapolator configuration for ITk
Cleanup extrapolator configuration for ITk:
- avoid separate configuration fragments
- make the tool private and configure it as public with clients if needed
- also cleanup
CaloExtensionBuilderAlgCfg
as the extrapolator was the only big dependency
A companion to !48415 (merged).
/cc @christos @tstreble @npetters @pagessin @lgagnon @nstyles