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

[origami-z]

Adding Calendar children API discussion here. children is not the only way to make "composition".

When picking the use of children, need to think about whether it's intuitive in relationship to the physical space, e.g. children for a Card is very clear that things would be put "inside" of card. Obviously in certain use cases (like lexical means not exactly the same).

In Calendar's case, is it clear without looking at actual render, that it's about adding something to the top section of calendar? <Calendar> xyz </Calendar> (intentionally use xyz to make the case, use Navigation makes it mixing API discussion)

Some potential alternative

1. Make it clear it's something like header, e.g., <Calendar Header={'xyz'} />, which Header could be swapped to be something different than the default navigation component. This means calendar can still be composed with other options
2. Continue to use children, but make both navigation and month view to be children. e.g.

   <Calendar>
     <CalendarNavigation />
     <CalendarMonthView />
   </Calendar>

[mark-tate]

We will push this to Core, once we have had feedback from stakeholders. Extending to end of Q3, we may release beforehand if we get the feedback we need

[ivan-calderon]

About date formatting @bhoppers2008 recently shared the following by email. "- Date should always default to a locale in format where month is always text.

• Never leave the date as numeric.
• Allow input in a number of different formats that default to the month as text.
• (Consider partial entry of DD MM–defaulting to current year)."

[ivan-calderon]

@mark-tate. In relation to the "tab order and focus pattern when confirmation pattern is used". It is working as intended in the examples. TYVM!

[mark-tate]

Frappe Goal: update in Labs with design feedback and then find Stakeholder feedback