Add support for v7 of the Rabbitmq client using pure async-await

[zlepper]

High level notes:

• PublisherConfirms seems to work vastly different now. Probably for the better, but it might conflict with some of Rebus expectations. I also haven't figured out how to weave in the expected timeout between the combination of "Publisher confirms", "Mandatory" and "Express" and now those 3 all fit together. Maybe you have some opinions?
• Batching is dead, the client handles that automatically now. See Remove batch publishing as its optimizations are now performed for "regular" publishes/outgoing frames rabbitmq/rabbitmq-dotnet-client#1028
• IModel (Now IChannel) is now considered thread safe with confirmation here: IChannel thread safety rabbitmq/rabbitmq-dotnet-client#1722 so we can get rid of the writer pool. I have tweaked some tests to ensure we actually survive reconnects even with this strategy.
• I got some old tests working by switching them to using testcontainers. That is not really relevant for this PR, however it did allow me to ensure the reconnection logic was sound.

I would recommend releasing this as a prerelease only for now if you merge it. 7.1 of the dotnet client for rabbitmq is around the corner (Expected in a week or two). And due to the rather large amount of changes here, we probably don't want people upgrading immediately :)

Closes #124

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[zlepper]

@mookid8000 hey :) any chance you can take a look at this and see if it looks reasonable? :)

[mookid8000]

Beautiful, thanks! 👍 It's out as Rebus.RabbitMq 10.0.0 on NuGet.org now 🙂

[zlepper]

Beautiful, thanks! 👍 It's out as Rebus.RabbitMq 10.0.0 on NuGet.org now 🙂

Excellent, Time to break production test this in confined and safe environments :D