wip: xxx: introduce a way to submit and listen isolated calls

[isidentical]

The idea underneath is, currently for every isolate run, you basically need two peers (a client and a server) which makes both sides hold state without a good reason. For the world of HTTP servers, we can essentially fire-and-forget (which is not a good name for this stuff where we actually care about the status of the task) them and let the gateway itself hold as little state/connections as possible.

For achieving this goal quickly, this PR proposes a Submit endpoint in addition to the existing Run endpoint in the isolate server where you can fire a task and pass a callback which will be used to communicate the logs and the results back. This is still a bit fragile (especially without any sort of fault tolarance on when the callback URL fails) and might be even slower (plain HTTP 🤢) but all of these properties can be improved upon once we are confident in the architecture. The main goal here is to provide the most basic form of fire-and-forget mechanism to isolate where we can start using and experimenting with it on the server and eventually make it nicer.

[kakkoyun]

/subscribe

[efiop]

Closing to continue in a separate PR (don't want to butcher content here).