Hardcode relay addresses in the builder

[ferranbt]

Right now, the user has to supply a list of configuration for all the builders he wants to connect to:

[[relays]]
name = "flashbots"
url = "https://0xac6e77dfe25ecd6110b8e780608cce0dab71fdd5ebea22a16c0205200f2f8e2e3ad3b71d3499c54ad14d6c21b41a37ae@boost-relay.flashbots.net"
priority = 0
use_ssz_for_submit = false
use_gzip_for_submit = false

Instead, we should built-in these configurations inside the rbuilder and let the user choose which one wants to use.

[bertmiller]

No strong feelings here. Maybe the compromise path could be allowing for custom relays in addition to the presets.

[ferranbt]

Yes, so now you have to do:

[[relays]]
name = "flashbots"
url = "https://0xac6e77dfe25ecd6110b8e780608cce0dab71fdd5ebea22a16c0205200f2f8e2e3ad3b71d3499c54ad14d6c21b41a37ae@boost-relay.flashbots.net"
priority = 0
use_ssz_for_submit = false
use_gzip_for_submit = false

[[relays]]
name = "relay-2"
url = "..."
priority = 0
use_ssz_for_submit = false
use_gzip_for_submit = false

[[relays]]
name = "relay-3"
url = "..."
priority = 0
use_ssz_for_submit = false
use_gzip_for_submit = false

With the new change you would something like this:

relays = ["flashbots", "relay-3"]

[[relays]]
name = "flashbots"
use_gzip_for_submit = true

[[relays]]
name = "relay-3"
url = "..."
priority = 0
use_ssz_for_submit = false
use_gzip_for_submit = false

You could even override some of the default presents.

[bertmiller]

Exactly