fix datepicker closing invoked by modal component

[k2s]

Proposed changes

Datepicker component is shown inside Modal component. Datepicker close method asks Modal component to close, but Modal doesn't informDatepicker that is is closed/hidden.

Main issue is with ESC keypress that is handled by Modal, but also programmatical closing of the Modal element will not correctly handle Datepicker closing.

Problems that is this causing:

• Year/Month select elements of Datepicker remains after ESC #6092 - if year/month dropdown is visible to user and ESC is pressed, it will close calendar, but the dropdown stays open
• onClose() callback is not fired when datepicker is closed with ESC #6500 - if ESC is pressed the Datepicker will not fire onClose event

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to change).

Checklist:

• I have read the CONTRIBUTING document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.