Add Upfront Shutdown Address to OpenChannelRequest

[carlaKC]

This PR adds an upfront shutdown address to lnrpc and lncli. Cooperative close out to these addresses is enforced provided that the remote peer supports the feature bit. The request will fail if an address is set for a peer that does not support upfront shutdown.

It also exposes the features that peers support in a new rpc endpoint GetFeatures so that users can check whether the peer supports the feature before setting the field (and check which features their node supports, if desired), which has the following output:

{
    "features": [
        {
            "bit": 5,
            "name": "upfront-shutdown-script",
            "is_required": false,
            "is_known": true
        },
        {
            "bit": 7,
            "name": "gossip-queries",
            "is_required": false,
            "is_known": true
        },
        {
            "bit": 9,
            "name": "tlv-onion",
            "is_required": false,
            "is_known": true
        },
        {
            "bit": 13,
            "name": "static-remote-key",
            "is_required": false,
            "is_known": true
        },
        {
            "bit": 0,
            "name": "data-loss-protect",
            "is_required": true,
            "is_known": true
        }
    ]
}

Fixes #3786

[carlaKC]

While working on a first iteration of this PR which had feature bits in ListPeers I picked up a race condition in our itests between connecting to a peer and handleInitMessage because remoteFeatures are only set on receipt of init so tests would panic on calls to ListPeers which had nil remoteFeatures. Not going to be a real world issue, just making a note of it here.

[carlaKC]

Rebased on #3824 to use common method, so first two commits are not up for review.

[cfromknecht]

@carlaKC clean pr! first two commits are in master now so we can rebase.

excited that we'll now have some moree insight into our peer's features. i wonder if maybe we should add the remote init features to listpeers as well? other than that, only a few small comments left.

[cfromknecht]

also note that #3837 proposes changing the rpc features to a map

[carlaKC]

also note that #3837 proposes changing the rpc features to a map

Given the addition of features to ListPeers and GetNode in #3837, I'm just going to add our own features to GetInfo, since peer features are sufficiently exposed.

[wpaulino]

LGTM. Needs a rebase due to a conflict and the commits from #3837 are still present in the branch.

[wpaulino]

Confirmed in a test environment I was only able to coop close out to the upfront address.

[carlaKC]

Rebased to address merge conflict 👮‍♀

[cfromknecht]

LGTM! 🥂 one small nit

[cfromknecht]

@carlaKC needs rebase