FR: Phase out hosted eth1 support

[prestonvanloon]

🚀 Feature Request

Description

Remove Prysmatic's hosted eth1 nodes as a default parameter.

Describe the solution you'd like

1. Log an error stating that the default Prysm nodes will be removed in the next release. It can go in the same block as this warning. (alpha.19)

prysm/beacon-chain/node/node.go

Line 469 in 7903ec0

log.Warn("Using default ETH1 connection provided by Prysmatic Labs. Please consider running your own ETH1 node for better uptime, security, and decentralization of ETH2. Visit https://docs.prylabs.network/docs/prysm-usage/setup-eth1 for more information.")

2. Remove default flag value, fail when unset. (alpha.20 or later)

Users could still opt to use Prysm's hosted nodes which will remain available for the foreseeable future, but they should not grow accustomed to this practice since we may not offer this service at mainnet launch.

Describe alternatives you've considered

We already display a warning, but users are still using Prysm's hosted eth1 nodes.
This may be because of a knowledge gap or a lack of willingness to run their own eth1 node.