Remove pluralization of failsafe metric namespace (open-telemetry#14722)

Author: trask

docs/instrumentation-list.yaml

@@ -3069,7 +3069,7 @@ libraries:
           type: STRING
         - name: failsafe.circuit_breaker.outcome
           type: STRING
-      - name: failsafe.circuit_breaker.state_changes.count
+      - name: failsafe.circuit_breaker.state_change.count
         description: Count of circuit breaker state changes.
         type: LONG_SUM
         unit: execution

instrumentation/failsafe-3.0/library/src/main/java/io/opentelemetry/instrumentation/failsafe/v3_0/FailsafeTelemetry.java

@@ -57,7 +57,7 @@ public <R> CircuitBreaker<R> createCircuitBreaker(
             .build();
     LongCounter stateChangesCounter =
         meter
-            .counterBuilder("failsafe.circuit_breaker.state_changes.count")
+            .counterBuilder("failsafe.circuit_breaker.state_change.count")
             .setDescription("Count of circuit breaker state changes.")
             .setUnit("{execution}")
             .build();

instrumentation/failsafe-3.0/library/src/test/java/io/opentelemetry/instrumentation/failsafe/v3_0/FailsafeTelemetryTest.java

@@ -67,7 +67,7 @@ void captureCircuitBreakerMetrics() {
         "io.opentelemetry.failsafe-3.0",
         metricAssert ->
             metricAssert
-                .hasName("failsafe.circuit_breaker.state_changes.count")
+                .hasName("failsafe.circuit_breaker.state_change.count")
                 .hasLongSumSatisfying(
                     sum ->
                         sum.isMonotonic()