[Service] Improve assertMetrics test function in service_test.go

[moh-osman3]

This issue is to track feedback provided about improving the assertMetrics() test function in service_test.go . This improvement is needed after adding instrumentation for proctelemetry.ProcessMetrics using otel-go, which breaks assertMetrics() when the featuregate is enabled. Otel metrics do not include the service* resource attributes with every metric and instead only records these attributes once in the otel_target_info.

The suggested improvement is to validate the metric values as well (since checking labels won't be helpful in the Otel case) and have two versions of assertMetrics. These functions should be named something like assertOCMetrics and asserOtelMetrics