feat: realtime v2 serializer

[edgurgel]

What kind of change does this PR introduce?

New V2 serializer that is a super set of the Phoenix V2 JSON Serializer. It has 2 special types of messages:

• User Broadcast Push
• User Broadcast

The clients will be able to send a new User Broadcast Push which allows for binary or JSON payloads. It allows for a more efficient handling of the user payload as well.

The backend will be able to then broadcast the User Broadcast Push as User Broadcast for the serializers with V2 while also being able to convert to the V1 Broadcast that Phoenix V1 JSON Serializer supports as long as the user payload is JSON.

If a binary payload is sent and there is a websocket using V1 listening it won't receive such message as only JSON is supported by V1.

This PR also add a new GitHub workflow to run integration tests with deno. Currently pointing to a realtime-js preview release for now.

And finally I fixed the Realtime Channel integration tests to run async as I'm now running them twice with each serializer and it was ultra slow to have them running synchronously:

Finished in 464.6 seconds (158.7s async, 305.9s sync)

Additional context

Connected to supabase/supabase-js#1829

[coveralls]

coverage: 87.096% (+0.2%) from 86.856%
when pulling eb5ed53 on feat/realtime-v2-serializer
into 9120f89 on main.

[filipecabaco]

our lib/realtime_web/channels/realtime_channel/message_dispatcher.ex is getting very complex we should take sometime to improve readability but later

[blacksmith-sh]

Found 2 test failures on Blacksmith runners:

Test	View Logs
test new/2 starts a new rate counter with sum limit to log (Realtime.RateCounterTest)	View Logs
test socket disconnect on jwt_secret the socket closes and sends a system message (Real time.Integration.RtChannelTest)	View Logs