api service /upstreams uses old default RPC nodes

[dboreham]

The node watcher service seems to take a list of "default nodes" then check to see which ones are live.
It has no way to discover more RPC nodes since the list of RPC service endpoints is not on chain.
The list of default nodes is hard wired into the source: https://github.com/0LNetworkCommunity/explorer/blob/main/api/src/node-watcher/node-watcher.service.ts#L15
This is all pretty bad because the list can (and has) become out of date.
Should at least be pulling the list from here: https://github.com/0LNetworkCommunity/seed-peers/blob/main/fullnode_seed_playlist.json