Support dot-separated OpenTelemetry metric names in OpenTelemetry output plugin

Use Case

We use Telegraf as an OpenTelemetry metrics pipeline component,
exporting metrics via OTLP to an OpenTelemetry-native backend.

Metrics are defined according to OpenTelemetry semantic conventions
(e.g. http.server.duration, http.client.request.count).

To keep metric naming consistent across the OpenTelemetry ecosystem,
it is important to preserve dot-separated metric names.

Expected behavior

Telegraf OpenTelemetry output should be able to emit metrics using
dot-separated names as defined by OpenTelemetry semantic conventions.

Ideally this would be configurable, for example:

• an option to preserve OTEL metric names
• or a naming mode (e.g. otel vs prometheus)/separator mode (e.g. . vs _)

Actual behavior

This also impacts existing dashboards and alerting rules,
as metric names emitted by Telegraf differ from
OpenTelemetry-recommended names.

As a result, dashboards and alerts defined using OTEL metric names
cannot be reused without manual renaming.

Additional info

Impact on production usage:

• Existing dashboards and alerting rules are built around
  OpenTelemetry semantic metric names
• Using Telegraf requires renaming metrics or duplicating dashboards
• This increases migration cost and risk of inconsistencies

Start by locating the OpenTelemetry output plugin and tracing how metric names are converted before export. Review the plugin's configuration and existing tests, then define the smallest supported naming option that preserves dot-separated names. Done means OpenTelemetry semantic names can be emitted without breaking the existing naming behavior.