Remove signal bootstrapping

[anacrolix]

Remove IpfsDHT.BootstrapOnSignal. This is behaviour that can be achieved without intruding on IpfsDHT. It's not used elsewhere. The tests are retained and adapted to work without the method.

[Stebalien]

I agree it doesn't really belong but... it's used in ipfs-cluster. cc @hsanjuan

[anacrolix]

There's a failing test but I believe it's unrelated, and I'm going to move on (and maybe fix that test in another PR).

[hsanjuan]

Hey, we use this. We need this. Why was this merged without even giving me the chance to explain why it's useful?

[hsanjuan]

At least explain what the workaround is.

[vyzo]

people please refrain merging those refactorings before the stakeholders can review!

[hsanjuan]

FYI, this is used because it is impossible to make the DHT do a bootstrap round at a certain moment. For example, if a new peer is added is added to a cluster, that peer needs to bootstrap ASAP, not wait for the next automatic bootstrap round. I don't think there is an equivalent way to manually trigger a bootstrap round.

[anacrolix]

@hsanjuan Thanks for the clarification. I don't find any other uses of BootstrapOnSignal other than the one in ipfs-cluster. It looks like the actual desired API is a synchronous Bootstrap method. I propose instead to add a method that does a single bootstrap synchronously.

[Stebalien]

@anacrolix In the future, please don't knowingly break someone else's code without their input (or very careful consideration).

[anacrolix]

This has been rolled into #225.