docs: add Redis and Kafka performance testing guides

[chideat]

What changed

• add a customer-facing Redis 7.2.15 performance testing guide for Sentinel and Cluster modes
• add an English Kafka performance testing guide; the documentation CI/CD pipeline handles Chinese localization
• cover both Kafka Raft metadata mode (KRaft) and legacy ZooKeeper-based Kafka deployments
• align ZooKeeper guidance with the product-facing RdsKafka API and its generated Strimzi resources
• document workload matrices, parameter-template selection, storage and PVC sizing, client and instance tuning, saturation criteria, monitoring, and report requirements
• provide executable Kafka 4.2 commands and a version-compatible Kafka 2.x command path for ZooKeeper-based operator releases
• keep both guides independent of private images and undocumented internal test implementations

Why

Customers need reproducible and auditable procedures based on community tools that can be mirrored into air-gapped environments and calibrated for different deployment sizes. The Kafka guide must also distinguish metadata modes because their topology, health evidence, operational constraints, and bundled client-script interfaces differ.

Impact

Documentation only. This PR does not change product code or runtime configuration.

Validation

Redis

• executed bounded Redis 7.2.15 Sentinel/RDB and Cluster/AOF workflow validation in a dedicated namespace
• exercised 512 B and 4 KiB values with pipeline depths 1 and 16
• verified the Prometheus export path for all 17 guide-required Redis metrics and target health
• verified CPU and memory utilization denominators against kube_pod_container_resource_limits
• scanned the guide for credentials, kubeconfig paths, registry details, private network addresses, Redis 8.x references, and obsolete Redis 6.0 template guidance

Kafka

• validated Kafka 4.2.0 topic, producer and consumer, KRaft quorum, ISR, consumer group, log directory, JMX, Kafka Exporter, Prometheus, and Kubernetes metric commands in an isolated business cluster
• reviewed the downstream Strimzi Kafka 2.x operator source for ZooKeeper replica, storage, generated-workload, metrics, upgrade-protocol, and legacy client-script behavior
• reviewed the rds-operator release-4.1 RdsKafka CRD, Kafka-version routing, ZooKeeper defaults, and generated Strimzi resource mapping
• passed go test ./controllers/strimzi in rds-operator
• verified Bash code blocks with bash -n
• built the complete documentation site successfully with yarn build
• passed git diff --check and completed terminology, factual, language, and sensitive-information review
• confirmed the published Kafka source contains no Chinese text or aKafka references
• ZooKeeper-mode commands have source/API compatibility validation but have not yet been executed end to end against a live ZooKeeper-based Kafka cluster

Scope

This PR intentionally contains only:

• docs/en/solutions/ecosystem/redis/Redis_Performance_Testing_Guide.md
• docs/en/solutions/ecosystem/kafka/Kafka_Performance_Testing_Guide.md

Validation reports, HTML, artifact JSON, CSV data, PromQL exports, and generator files are not included.