remove regular expression substitution in _instance_name

[lucabello]

Enhancement Proposal

When returning the _instance_name, we currently do a regex substitution to only keep ASCII character in label values.

However, according to the docs we link to, it explicitly mentions that label values can be unicode character.

[sabaini]

Heya, for addtl context I believe this was introduced here in the course of fixing #60

[sed-i]

Yep, probably a confusion on my part. To summarize the doc:

• Metric name: [a-zA-Z_:][a-zA-Z0-9_:]*
• Label name (key): [a-zA-Z_][a-zA-Z0-9_]*
• Label value: may contain any Unicode characters