[Tracking Issue] Shutdown PL-hosted delegated and preload nodes

[BigLep]

This is a tracking issue for shutting down the PL-hosted delegate and preload nodes that are relied upon currently by js-ipfs. This is discussed in https://blog.ipfs.tech/state-of-ipfs-in-js/#pl-delegate-and-preload-nodes-will-be-shutting-down

This issue needs to be fleshed out with specific steps (including communication) and timeline, but for now is serving as a tracking issue that can link to.

• Establish a dedicated /routing/v1 endpoint: Expose trustless gateway and delegated routing under new domains with certain policies  ipshipyard/waterworks-community#1
• Write a blog entry announcing the deprecation
• Have the existing preload domains/paths return an error page

[SgtPooki]

From @lidel in slack:

The cavat here is that preload nodes are also used as legacy (pre-IPNI) nodeX.delegate.ipfs.io routing nodes that expose /api/v0/dht/* and used by:

• https://github.com/libp2p/js-libp2p-delegated-peer-routing
• https://github.com/libp2p/js-libp2p-delegated-content-routing/
• Rhea (bifrost-gateway uses them for fetching signed IPNS Records, because cid.contact does not support that yet (IPIP-379)

[BigLep]

Discussion of preload nodes from docs.ipfs.tech were stripped out in ipfs/ipfs-docs#1620

[BigLep]

We're a step closer to getting preload nodes removed with establishing a /routing/v1 endpoint that can be used for delegated routing: ipshipyard/waterworks-community#1