Move DatePicker, Calendar and DateInput to Core

[mark-tate]

DatePicker, Date Input and Calendar are in Labs, ready for promotion to Core, once we have some user-feedback from Stakeholders.

This PR should collate the known issues/discussions, so we make sure we move a stable feature set to Core.

• Confirm the tab order and focus pattern when confirmation pattern is used @ivan-calderon
• US date formatting requires a comma, confirm how US dates should be entered and formatted. @ivan-calderon
• A11y SME review, what is the gap to both WCAG 2.1 AA and also WCAG 2.2 AA ?
• Overlay discussion, is there some functionality we are missing in Core