Date/time field exposure

Problem/Motivation

Part 6 of splitting #3595219: 3.0 Exploration. This issue exposes the configuration of the date and time element family (date, time, datetime, datelist) for querying. Submission parsing/validation for these elements is intentionally split into a follow-up (part 7) to keep each piece reviewable.

Missing in 3.x:

• time: min, max, step.
• date: the date-specific configuration fields and the default value.
• datelist / datetime: which date/time parts are shown, the part order, and the per-part title display.

Proposed resolution

• Expose time min / max / step.
• Expose the date element fields and resolve its default value correctly (building on the default-value producer from #3598935: Improve cacheability and rendering).
• Expose the datelist/datetime fields, backed by new enums for the date parts and their title display: WebformDatePart, WebformDatePartTitleDisplay, WebformDatetimeDateElement, WebformDatetimeTimeElement.

This is read-only field exposure via WebformElementMetadata.php and the schema builder; no submission logic changes here.

Remaining tasks

• Add enums WebformDatePart, WebformDatePartTitleDisplay, WebformDatetimeDateElement, WebformDatetimeTimeElement under src/Enum/; wire into WebformSchemaBuilder.php.
• Expose time/date/datelist fields in WebformElementMetadata.php and WebformExtension.php; resolve the date default value.
• Tests: TimeTest, DateBasedElementsTest, DateExtrasTest, DatelistTest, plus the time.gql / datelist.gql / datetime_extras.gql fixtures and shared test-form additions.

API changes

Additive: new fields on time / date / datelist / datetime elements and the supporting date-part enums. No fields removed.

Release notes snippet

Date and time elements now expose their configuration — time min/max/step, date fields and default value, and the datelist/datetime parts, order and per-part title display.