Implement gossipsub IDONTWANT (#5422)

* move gossipsub into a separate crate

* Merge branch 'unstable' of github.com:sigp/lighthouse into separate-gossipsub

* update rpc.proto and generate rust bindings

* gossipsub: implement IDONTWANT messages

* address review

* move GossipPromises out of PeerScore

* impl PeerKind::is_gossipsub

that returns true if peer speaks any version of gossipsub

* address review 2

* Merge branch 'separate-gossipsub' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* Merge branch 'unstable' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* add metrics

* add tests

* make 1.2 beta before spec is merged

* Merge branch 'unstable' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* cargo clippy

* Collect decoded IDONTWANT messages

* Use the beta tag in most places to simplify the transition

* Fix failed test by using fresh message-ids

* Gossipsub v1.2-beta

* Merge latest unstable

* Cargo update

* Merge pull request #5 from ackintosh/impl-gossipsub-idontwant-ackintosh-fix-test

Fix `test_ignore_too_many_messages_in_ihave` test

* Merge branch 'unstable' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* update CHANGELOG.md

* remove beta for 1.2 IDONTWANT spec has been merged

* Merge branch 'unstable' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* Merge branch 'impl-gossipsub-idontwant' of github.com:jxs/lighthouse into impl-gossipsub-idontwant

* Merge branch 'unstable' of github.com:sigp/lighthouse into impl-gossipsub-idontwant

* improve comments wording

* Merge branch 'impl-gossipsub-idontwant' of github.com:jxs/lighthouse into impl-gossipsub-idontwant

Cargo.toml

@@ -126,6 +126,7 @@ fnv = "1"
 fs2 = "0.4"
 futures = "0.3"
 hex = "0.4"
+hashlink = "0.9.0"
 hyper = "1"
 itertools = "0.10"
 lazy_static = "1"