v1.17: Make the quic server connection table use an async lock, reducing thrashing (backport of #293)

[mergify]

Problem

Usage of sync locks on the quic server can cause thrashing when under lock contention

Summary of Changes

Use async lock

Fixes #

---

This is an automatic backport of pull request #293 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 36e9765 has failed:

On branch mergify/bp/v1.17/pr-293
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Unmerged paths:
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	both modified:   streamer/src/nonblocking/quic.rs

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To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[t-nelson]

lgtm. @sakridge for stable bp approval

[sakridge]

lgtm