service: simplify Logs() & improve docs

[ilgooz]

No description provided.

[NicolasMahe]

I have a question that is related to logs but not blocking for this PR.

https://github.com/mesg-foundation/core/blob/1ecd99db1c8c90a60231d77f8e857309c45ddf35/service/logs.go#L23-L58

Seeing this function, I don't see anything that will make the core to 'stop' listening the logs when let's say the user stops the command service logs. I think the go routine will continue to live forever..
Am I right or there is a mechanism that will stop the stream of logs?

[ilgooz]

@NicolasMahe goroutine will eventually be closed when these writers closed inside grpc core pkg by the api cancellation.

but we should definitely improve it later to close the reader as well.

-i'm actually thinking about creating a custom io.Closer to simplify the process. and, not relevent with this but I also plan to do even more and improve the chunker pkg to implement custom io.Writers/Readers and simplify log streams all once. these are some future refactoring plans.

because for now, stdcopy will only be able to cancel after reading from the reader and trying to write to the closed writers(writers closed when their readers are closed -io.Pipe()-). but we can make it cancel sooner by closing the reader as well so it doesn't need to wait data to appear in the reader.