Introduce PrometheusMetricAssert and update metrics ITs for name compatibility

[SavitarC]

Motivation

• Ensure tests detect Prometheus metrics across legacy and new naming conventions by resolving compatible metric names and kinds.
• Make integration tests more robust to cross-registry name changes (dots vs. snake_case and _total suffix behavior).

Description

• Add PrometheusMetricAssert utility with MetricKind enum and logic to resolve legacy and new Prometheus-compatible names and to assert metric presence via assertDubboMetricExposed.
• Replace plain metric string checks in ProviderMetricsIT and ConsumerMetricsIT with a MetricExpectation holder and helper methods addGauge/addCounter to record raw metric names and expected kinds.
• Update test assertion loops to call PrometheusMetricAssert.assertDubboMetricExposed and log missing rawName and kind for clearer diagnostics.
• Add comments clarifying when to use explicit kinds to preserve cross-registry compatibility.

Testing

• Ran the modified integration tests ProviderMetricsIT and ConsumerMetricsIT, which exercise the /metrics scrape parsing and compatible-name assertions, and both tests passed.
• Existing automated test execution completed without failures for the modified modules.

---

Codex Task