Attempt connections in parallel

[Jake-Shadle]

This fixes an issue where attempting a connection to more than 1 remote endpoint would be done serially, thus the backoff would apply to all endpoints, rather than increasing for each individual one. This changes it so that the connections are attempted in parallel, choosing whichever successful connection is made first, and applying the backoff to each parallel attempt, rather than each individual attempt.

[quilkin-bot]

Build Succeeded :partying_face:

Build Id: 5f50de56-5ff5-47e5-abf5-431c1bc48202

The following development images have been built, and will exist for the next 30 days:

• us-docker.pkg.dev/quilkin/ci/quilkin:0.10.0-dev-ad0865b

To build this version:

git fetch [email protected]:googleforgames/quilkin.git pull/1244/head:pr_1244 && git checkout pr_1244
cargo build

[Jake-Shadle]

Hmm, maybe I'm misremembering and it was working.