fix(metrics): Prometheus metrics output

[m3diumrare]

After the sei-chain to sei_chain prefix change in #3554, it surfaced that otel labels also had invalid Prometheus label characters ('.')

Tested on local Sei node, with this patch the Prometheus remote write endpoint no longer drops any metrics from the node.

Example before:

curl -si -H "Accept: application/openmetrics-text;version=1.0.0;escaping=allow-utf-8" http://127.0.0.1:26660/metrics | grep 'telemetry.sdk.language'
target_info{"service.name"="unknown_service:seid","telemetry.sdk.language"="go","telemetry.sdk.name"="opentelemetry","telemetry.sdk.version"="1.39.0"} 1

after:

 curl -si -H "Accept: application/openmetrics-text;version=1.0.0;escaping=allow-utf-8" http://127.0.0.1:26660/metrics | grep 'telemetry.sdk.language'
target_info{service_name="unknown_service:seid",telemetry_sdk_language="go",telemetry_sdk_name="opentelemetry",telemetry_sdk_version="1.39.0"} 1

[cursor]

PR Summary

Low Risk
Observability-only change to metric name/label translation; no consensus, auth, or transaction logic affected.

Overview
Fixes Prometheus remote write dropping node metrics by configuring both OTel→Prometheus exporters to use UnderscoreEscapingWithSuffixes when translating OTel metric and label names.

SetupOtelPrometheus (sei-db/common/metrics/setup.go) and SetupOtelMetricsProvider (utils/metrics/metrics_util.go) now pass prometheus.WithTranslationStrategy(otlptranslator.UnderscoreEscapingWithSuffixes) (or the otel exporter equivalent). That rewrites invalid label characters—such as dots in OTel attributes—into Prometheus-safe names, which addresses fallout from the earlier sei-chain → sei_chain namespace change.

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[m3diumrare]

@philipsu522 this would be great to get into 6.6 release if possible