Better validation of the pipeline_id

[elasticmachine]

Original comment by @ph:

With the issue LINK REDACTED we have added better validation concerning the uniqueness of the defined values for the config management.

But this is not enough, currently, our pipeline_id is not really well defined inside logstash and we are really liberal in the accepted string. We accept anything that can be valid unicode.

With the move to more centralized configuration and multiple pipelines we need to make sure that the format for that string is more strict and well defined.

This problem need to be solved inside core, but I've created this issue to track it in x-pack too.

Original LS issue:#8164