Add --network and --datadir to help text of trustedNodeSync

[yorickdowne]

Feature: Add the --network and --datadir options to the help text for trustedNodeSync. It currently reads:

nimbus_beacon_node trustedNodeSync [OPTIONS]...

The following options are available:

     --trusted-node-url        URL of the REST API to sync from
                               [=http://localhost:5052].
     --blockId                 Block id to sync to - this can be a block root,
                               slot number, "finalized" or "head" [=finalized].
     --backfill                Backfill blocks directly from REST server instead
                               of fetching via API [=true].

[arnetheduck]

blocked on status-im/nim-confutils#29

[jclapis]

Ran into this too when adding checkpoint sync support to Rocket Pool. Not a huge deal because you can tell pretty clearly what's going on from the logs, but it would have been helpful when I started.