feat(ui5-datepicker): implement valuestatemessage slot

[fifoosid]

🎉

[fifoosid]

Fixes #1385

[ilhan007]

Two comments:

• If the valueStateMessage content/text is changed when it is opened, the change would not be applied as we display a copy/clone, but it`s rather unusual, in most cases it would be fine as whenever the input field is clicked, the component is being invalidated and the valueStateMsg is up to date. @vladitasev what do you think, should we observe the original.

• when I click the toggle icon, the value state msg is shown for a second and then the calendar is displayed as usual, I did not check how it works in openui5 (might be the same), but it looks strange, almost like a bug, because something blinks for a moment and it`s gone.

[fifoosid]

The second comment is fixed, and the first one I would rather not implement until someone needs it.

[ilhan007]

Two comments:

• in phone mode the Input with suggestions and value state msg throws error, because the inputDomRef is not there ( in phone mode)
• should we displayed the value state msg of DatePicker within the dialog in phone mode as well?

[ilhan007]

With the current changes in the Input.js the following stops working: previously the value state message used to be displayed in the dialog on phone, now - it is not. If for the DatePicker that is fine, I think the Input should show the message within the dialog, at least it was intentionally implemented in this way.

[vladitasev]

The link inside does not work, when you click it, it does not change the URL, but closes the popup instead.

tested now works fine