Sanitize metric names in the prometheus exporter

[dmathieu]

Prometheus has different metric restrictions than the specification provides us.
All prometheus metrics must match this regex: https://github.com/prometheus/common/blob/main/model/metric.go#L27

While the specification will use dots in metric names, and therefore cause invalid metric names in the exporter.
See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/semantic_conventions/process-metrics.md

With this change, libraries can use metric names valid with semantic conventions, for which any invalid character will be replaced with an underscore.

Related: open-telemetry/opentelemetry-go-contrib#2787

Fixes #3183

[codecov]

Codecov Report

Merging #3212 (2822387) into main (2ae5922) will increase coverage by 0.0%.
The diff coverage is 97.5%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3212   +/-   ##
=====================================
  Coverage   77.3%   77.3%           
=====================================
  Files        159     159           
  Lines      11101   11139   +38     
=====================================
+ Hits        8583    8617   +34     
- Misses      2323    2325    +2     
- Partials     195     197    +2     

Impacted Files	Coverage Δ
exporters/prometheus/exporter.go	78.5% <97.5%> (+1.6%)	⬆️
sdk/trace/batch_span_processor.go	81.9% <0.0%> (+0.8%)	⬆️

[MadVikingGod]

I think this is a good stop gap, but it will iterate through all names on every collect.

We should revisit this and see if there is a way to optimize it so that there is approximately constant time sanitizing the names.

[MrAlias]

🥇