feat(temporal): add composite metric (backlog + running workflow count)

[SanilK2108]

• Add includeRunningWorkflowCount (default: true) to use backlog + running workflow count as the scaling metric, avoiding premature scale-down when workers are fast and backlog is often zero.
• Add optional workflowTaskQueueForCount to scope running count by workflow task queue (e.g. when scaling activity workers).
• getRunningWorkflowCount() uses CountWorkflow with visibility query ExecutionStatus = 'Running' AND TaskQueue = ''.
• On CountWorkflow failure, fall back to backlog-only and log at V(1).
• Add tests for new metadata and default composite behavior.

Ref: #7459

Provide a description of what has been changed

Checklist

• When introducing a new scaler, I agree with the scaling governance policy
• I have verified that my change is according to the deprecations & breaking changes policy
• Tests have been added (if applicable)
• Ensure make generate-scalers-schema has been run to update any outdated generated files
• Changelog has been updated and is aligned with our changelog requirements, only when the change impacts end users
• 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)
• Commits are signed with Developer Certificate of Origin (DCO - learn more)

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[rickbrouwer]

duplicate: #7460