fix(spanner): clear metrics tracers after operation completion (#8172)

Allow MetricsTracerFactory.clearCurrentTracer to accept the already-extracted operation request id stored on MetricsTracer. This ensures completed operations remove their tracer entries instead of retaining them until the periodic cleanup threshold.

Author: rahul2393

handwritten/spanner/src/metrics/metrics-tracer-factory.ts

@@ -305,7 +305,8 @@ export class MetricsTracerFactory {
    * @param requestId The request id of the gRPC call set under 'x-goog-spanner-request-id'.
    */
   public clearCurrentTracer(requestId: string) {
-    const operationRequest = this._extractOperationRequest(requestId);
+    const operationRequest =
+      this._extractOperationRequest(requestId) || requestId;
     if (!this._currentOperationTracers.has(operationRequest)) {
       return;
     }

handwritten/spanner/test/metrics/metrics-tracer-factory.ts

@@ -158,6 +158,22 @@ describe('MetricsTracerFactory', () => {
     assert.ok(tracer);
   });
 
+  it('should clear a MetricsTracer using an extracted operation request id', () => {
+    const factory = MetricsTracerFactory.getInstance('project-id');
+    factory!.createMetricsTracer(
+      'some-method',
+      'method-name',
+      '1.1a2bc3d4.1.1.1.1',
+    );
+
+    assert.strictEqual((factory as any)._currentOperationTracers.size, 1);
+
+    factory!.clearCurrentTracer('1.1a2bc3d4.1.1.1');
+
+    assert.strictEqual((factory as any)._currentOperationTracers.size, 0);
+    assert.strictEqual((factory as any)._currentOperationLastUpdatedMs.size, 0);
+  });
+
   it('should correctly set default attributes', () => {
     const factory = MetricsTracerFactory.getInstance('project-id');
     const tracer = factory!.createMetricsTracer(