Support UTF-8 label and metric names

[yeya24]

This is the tracking issue for supporting UTF-8 label and metric names. See upstream Prometheus issue for context: prometheus/prometheus#13095.

Most of the work has already been done in upstream Prometheus and common libraries. The main work left is more of enabling the feature, compatibility and validations.

[stale]

This issue has been automatically marked as stale because it has not had any activity in the past 60 days. It will be closed in 15 days if no further activity occurs. Thank you for your contributions.

[yeya24]

still valid