Drop Rialto <> Millau bridges

[svyatonik]

We already have some troubles with maintaining those bridges (#2647 (review)).

Since we already have a live setup (Rococo <> Wococo), which will be superseded with Rococo <> Westend bridge soon AND at least we have some basic zombienet tests, I think the time has come to drop Rialto and Millau (and test deployments VM).

Couple of things to mention:

• also removed several unused subcommands of substrate-relay binary;
• also removed several scripts that will be unneeded after we'll move to polkadot-sdk;
• also removed fuzzer that has never been used;
• left the only docker image that should be built from this repo - the one with substrate-relay binary. We'll need to have a similar build step in polkadot-sdk, but until that, we'll be building it from here.

[bkontur]

@svyatonik Slava, you should write some condolence speech for Millau and Rialto :(,
Maybe I asked that before, but who and why did choose those names?

Will do the same for `polkadot-staging?

[svyatonik]

@svyatonik Slava, you should write some condolence speech for Millau and Rialto :(, Maybe I asked that before, but who and why did choose those names?

Will do the same for `polkadot-staging?

Let's just move forward with that. I think @tomusdrw was behind that :) Just some bridges (https://en.wikipedia.org/wiki/Rialto_Bridge + https://en.wikipedia.org/wiki/Millau_Viaduct)

[acatangiu]

40K lines fewer to maintain ❤️

[tomusdrw]

@svyatonik Slava, you should write some condolence speech for Millau and Rialto :(, Maybe I asked that before, but who and why did choose those names?
Will do the same for `polkadot-staging?

Let's just move forward with that. I think @tomusdrw was behind that :) Just some bridges (https://en.wikipedia.org/wiki/Rialto_Bridge + https://en.wikipedia.org/wiki/Millau_Viaduct)

Indeed :)