Cleanup metric names inside scalers

[JorTurFer]

After #2123, we can ensure that metric names are unique inside ScaledObject. Before it, we used several mechanism inside scalers to avoid conflicts in metric names (like adding part of masked connectionString) those are not needed right now.
IMHO, we should review all scalers and remove those mechanisms. This will clear the code, unify how we are calculating metric names, and reduce risks related with exposing secrets

These listed metrics are the expected result for each scaler:

• Artemis: sx-artemis-{queueName}
• Apache Kafka: sx-kafka-{topic}
• AWS Cloudwatch: sx-aws-cloudwatch-{dimensionName}
• AWS Kinesis: sx-aws-kinesis-{streamName}
• AWS SQS: sx-aws-sqs-{queueName}
• Azure Blob: sx-azure-blob-{blobContainerName | customUserName}
• Azure EventHub: sx-azure-eventhub-{eventhubConnection}
• Azure Log Analytics: sx-azure-log-analytics-{workspaceId | customUserName} (No changes)
• Azure Monitor: sx-azure-monitor-{azureMonitorName}
• Azure Pipelines: sx-azure-pipelines-{poolId}
• Azure Service Bus: sx-azure-servicebus-{queueName | topicName}
• Azure Storage Queue: sx-azure-queue-{queueName}
• Cassandra: sx-cassandra-{keyspace | customUserName} (No changes)
• Cron: sx-cron-{timezone}-{start}-{end} (No changes)
• External: sx-{metricName} (No changes)
• Google Cloud Platform‎ Pub/Sub: sx-gcp-ps-{subscripotionName} (No changes)
• Graphite: sx-graphite-{metricName} (No changes)
• Huawei Couldeye: sx-huawei-cloudeye-{metricName}
• IBM MQ: sx-ibmmq-{queueName}
• InfluxDB: sx-influxdb-{organizationName | userCustomName}
• Kubernetes Workload: sx-workload-{namespace}
• Liiklus Topic: sx-liiklus-{topic}
• Metrics API: sx-metric-api-{valueLocation}
• MongoDB: sx-mongodb-{collection | userCustomName}
• MSSQL: sx-mssql-{database | host | customUserName}
• MySQL: sx-mysql-{dbName} (No changes)
• NAT Streaming: sx-stan-{subject}
• OpenStack Metric: sx-openstack-metric-{metricId}
• OpenStack Swift: sx-openstack-swift-{metricName}
• PostgreSQL: sx-postgresql{ |-userCustomName}
• Prometheus: sx-prometheus-{metricName}
• RabbitMQ: sz-rabbitmq-{queueName | userCustomName}
• Redis Lists: sx-redis-{listName} (No changes)
• Redis Lists Cluster: sx-redis-{listName} (No changes)
• Redis Streams: sx-redis-streams-{streamName}
• Redis Streams Cluster: sx-redis-streams-{streamName}
• Selenium Grid Scaler: sx-seleniumgrid-{browserName}
• Solace PubSub: sx-solace-{queueName}-{metricType}

Checklist

• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• Tests have been added
• A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on (repo) (if applicable) docs: Cleanup metric names inside scalers keda-docs#576
• Changelog has been updated

Fixes #2191

[JorTurFer]

/run-e2e

[JorTurFer]

Could you take a look and share your thoughts @zroubalik ?
If you agree with the cleanup, I will open this as PR and modify the docs

[JorTurFer]

InfluxDB e2e test has a timeout during the startup, but it works.
Maybe we could increase the timeout from 180 sec to (IDK) 300

[JorTurFer]

/run-e2e solace.test.ts

[JorTurFer]

/run-e2e

[zroubalik]

@JorTurFer looking great!

I like the unification. I'd do a few minor changes:

• Metrics API: sx-http-{valueLocation} -> sx-metric-api-{valueLocation} So it is not confused with the HTTP Add On or any other potential HTTP based scaler.
• Google Cloud Platform‎ Pub/Sub: sx-gcp-{subscripotionName} -> sx-gcp-ps-{subscriptionName} To mark that it is GCP Pub/Sub one.

[JorTurFer]

@zroubalik PTAL
I applied the feedback and I added a test to validate GetMetricSpecForScaling in metrics-api because we didn't have it yet.
Related with e2e tests, I have tried several times and except solacer (which failed because it was wrong, and it's already fixed), the others fails randomly

[zroubalik]

@JorTurFer the following job has been canceled, because of an action on this PR: https://github.com/kedacore/keda/actions/runs/1439326562