otelconf: fix Prometheus reader converting dot-style labels to underscores

[dmitryax]

When both without_type_suffix and without_units are set (which is the default config for the OTel Collector), prometheusReaderOpts was selecting UnderscoreEscapingWithoutSuffixes as the translation strategy. This strategy sets LabelNamer{UTF8Allowed: false}, converting OTel dot-style label names (e.g. service.name) to underscore-style (service_name) in target_info and on all metric datapoints.

Fix by using NoTranslation instead, which preserves dot-style label names (ShouldEscape()=false) and suppresses metric name suffixes (ShouldAddSuffixes()=false).

The restored behavior is close to what we had before #8595.

Related issue: open-telemetry/opentelemetry-collector-contrib#47011

I manually tested it and it solves the issue above for the collector

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.1%. Comparing base (529b99f) to head (a395b37).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8696   +/-   ##
=====================================
  Coverage   82.1%   82.1%           
=====================================
  Files        183     183           
  Lines      13790   13790           
=====================================
  Hits       11332   11332           
  Misses      2054    2054           
  Partials     404     404           

Files with missing lines	Coverage Δ
otelconf/v0.3.0/metric.go	89.7% <100.0%> (ø)

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[XSAM]

Should we verify the body contains target_info and not contains the target.info? This prevents MetricNamer accidentally takes TranslationStrategyOption.NoTranslation seriously in the future.

[dmathieu]

See collector upgrade slack thread: https://cloud-native.slack.com/archives/C02JJK840SH/p1773874400856229

I agree with @codeboten's comments on that thread. When setting up the prometheus exporter, we should follow the prometheus conventions, not enforce the OTel ones.

[MrAlias]

cc @dashpole

[dashpole]

Is the collector able to use NoTranslation if it wants this behavior? Escaping to underscores is the correct default behavior according to the prometheus sdk exporter spec.

[dmitryax]

This is just an attempt to address a regression on the collector side appeared in 0.148.0 release when instead of getting the following resource for internal collector metrics

Resource attributes:
     -> service.name: Str(otelcontribcol)
     -> service.instance.id: Str(35ccf925-339a-47e6-a3f8-043013267950)
     -> server.port: Str(8888)
     -> url.scheme: Str(http)
     -> service.version: Str(0.147.0-dev)

we started getting

Resource attributes:
     -> service.name: Str(otel-collector)
     -> service.instance.id: Str(0.0.0.0:8888)
     -> server.port: Str(8888)
     -> url.scheme: Str(http)
     -> service_instance_id: Str(09da6493-2d67-4201-b962-8396ba5c5618)
     -> service_name: Str(otelcontribcol)
     -> service_version: Str(0.148.0-dev)

with the collector's default configuration.

According the @dmathieu this can be resolved by moving collector go sdk config to 1.0. If that better way, I'm happy to close this PR.

For now I've marked this issue as a collector release blocker