Add test case for BuildCompliantMetricName with a metric that starts with a digit and addMetricSuffixes is true

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Author: ArthurSens

otlptranslator/metric_name_builder_test.go

@@ -238,6 +238,14 @@ func TestBuildCompliantMetricName(t *testing.T) {
 			addMetricSuffixes: false,
 			expected:          "_5xx_errors",
 		},
+		{
+			name:              "metric name starting with digit, with suffixes",
+			metricName:        "5xx_errors",
+			unit:              "",
+			metricType:        MetricTypeMonotonicCounter,
+			addMetricSuffixes: true,
+			expected:          "_5xx_errors_total",
+		},
 		{
 			name:              "metric name with multiple consecutive invalid chars",
 			metricName:        "api..//request--time",