Make Release date range End date accessible in worksheet equations and field identifiers

Currently, the End date from the Release date range field cannot be referenced in custom worksheet equations, or automation rules. The field identifier documentation only provides access to start_date, release_date, and external_release_date for releases, but not the End date portion of the date range field.

Without access to the date range End date, users cannot create proactive validation warnings when dates are misaligned (e.g., when an internal completion date exceeds the planned End date)

Add end_date as an accessible field identifier for Release records in worksheet equations and automation rules.