Strict schema rules and new methods for Workload Capture

Several fields within the WorkloadCapture, StartWorkloadReplayContext, and StopWorkloadReplayContext schemas (such as workloadId, startTime, endTime, and sourceInstance) have transitioned to read-only or immutable status. Additionally, parameters like project, instance, and workloadId are now strictly required across related endpoints. On the feature side, new endpoints under resources.workloadCaptures (list, start, stop, startReplay) have been formally added, enabling developers to capture production query traffic and safely replay it on test instances to evaluate performance impacts or database upgrades.