Add table-backed BDD step for Helm function creation

Description

The BDD suite has a table-backed step for image-based function creation, but Helm-based function scenarios must use a long raw nvcf-cli function create command. This exposes command construction in product-readable feature files and makes chart options difficult to review.

Add a table-backed function creation step for Helm charts. It should provide the same readable option table used by the existing image-based create and function deploy steps while preserving exact CLI argument coverage in unit and wiring tests.

Definition of Done

• Add a reusable Gherkin step for creating a Helm chart function with CLI options in a table.
• Use the step in the single-cluster and multi-cluster Helmfile scenarios.
• Preserve support for the chart reference, chart service, inference endpoint, and health endpoint options.
• Add step-level tests for option ordering, interpolation, quoting, and command failures.
• Keep the feature scenarios declarative and readable without weakening their outside-in live coverage.
• Update BDD contributor guidance if the new step changes the documented DSL.

Resources (optional)

• #1865

By submitting this issue, you acknowledge that you are an assigned member of the NVCF development team and agree to follow our code of conduct and our contributing guidelines.

Start by locating the existing table-backed image-based function-creation step and its step-level tests, then trace the single-cluster and multi-cluster Helmfile scenarios. Compare their option handling and use the BDD contributor guidance as the documentation entry point. Done means readable declarative scenarios, coverage for ordering, interpolation, quoting, and failures, preserved Helm options, and updated guidance if needed.