Unlocking workflow flexibility with variable-sharing between parent and child pipelines

Introduces the ability to pass variables from parent pipeline steps to child pipelines using the `input-variables` section in the parent step's YAML configuration. This allows for dynamic configuration and data sharing between orchestrated pipeline stages, with support for static values, repository variables, and workspace variables. Includes limitations on security (not for secrets), a maximum of 20 input variables, and validation rules for variable keys and values.