feat(splunk-o11y): add Forge impact dynamic variables

[edersonbrilhante]

Description

Adds dynamic dashboard variable support to the ForgeCICD Impact dashboard in the shared Splunk Observability configuration module.

• Adds the dynamic_variables input to the forge_impact dashboard submodule.
• Renders each provided dynamic variable on the Signalfx dashboard.
• Adds optional parent dashboard_variables.forge_impact support while falling back to the existing runner K8S tenant names for current callers.
• Regenerates the shared module README.

Type of Change

• Feature
• Bug Fix
• Documentation
• Refactor
• Other: ________

Testing

• terraform fmt -check modules/integrations/splunk_o11y_conf_shared/variables.tf modules/integrations/splunk_o11y_conf_shared/dashboards.tf modules/integrations/splunk_o11y_conf_shared/dashboards/forge_impact/main.tf modules/integrations/splunk_o11y_conf_shared/dashboards/forge_impact/variables.tf
• git diff --check
• Commit pre-commit hooks passed, including Terraform/Tofu fmt and validate hooks.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None