Add live_component update telemetry event

[bamorim]

The second part of what was discussed on this thread. This together with #2907 will already give good hooks for traces to be able to correlate nested component renders.

For this one, I decided to group cid, socket, assigns and whether the component is new or not in a list of maps to make life easier for whoever is consuming this.

I took the opportunity to do a slightly refactor to make the "shape" of assigns_sockets uniform regardless of whether the component have update_many exported or not. This was done simply by just adding {new_assigns, socket} to the assigns_sockets in the inner reduce and then calling update after inside a map call.

[josevalim]

This code can be very performance sensitive. Doing all of these traversals for telemetry purposes is going to be expensive. We can start with a single telemetry passing :component and :assigns_sockets as metadata.

[bamorim]

Fair enough, I thought about passing metadata (the internal "variable") , but that would probably be leaking an internal structure, so I did this.
I'll change to just pass the assigns_sockets. On the stop event, do you think I should replace sockets or just add a new metadata field with the new sockets?

[josevalim]

Just return the new sockets and the component, yeah.

[bamorim]

Done 😄

[josevalim]

Can you please revert the other changes to the file and keep it a simple wrapper around the existing calls?

[bamorim]

Can you please revert the other changes to the file and keep it a simple wrapper around the existing calls?

But the refactor of making assigns_sockets is necessary, otherwise the render would be happening in the the inner loop and we would not be able to send assigns_sockets in the telemetry metadata. Also arguably it is a little bit better IMHO since before when no update_many was defined, the name assigns_sockets was actually just the resulting sockets, so it was not a clear naming.

I can revert other small changes, but this is already the bulk of the changes.

[bamorim]

I'll try to remove as much of unnecessary changes as possible, though.

[josevalim]

I see, that makes sense. Thank you! 💚 💙 💜 💛 ❤️