bug(datepicker): Datepicker w/ date range It is not providing audio feedback of whether the date selection is start date or end

[zarend]

Copied from internal bug report

Environment:
OS| Browser | Screen reader
ChromeOS | Google Chrome 91.0.4472.167 | ChromeVox
macOS Catalina | Google Chrome 92.0.4515.131 | VoiceOver
Windows 10 | Google Chrome 92.0.4515.131 | NVDA/JAWS
Windows 10 | Firefox 90.0.2 (64-bit) | NVDA

Pre-requisites:

1. Enable the respective screen reader

Steps

1. Browse the Datepicker demo
2. Navigate to the "Date range selection" section
3. Activate "Open calendar" button from date range section, say, "Date range selection"
4. Activate any start date
5. Focus on any date to select end date

Actual result:
It is not providing any audio feedback on whether selection is for start date or end date

EXPECTED result:
It should provide audio feedback that calendar is open for start date selection. And on selection of the start date, it should provide audio feedback that calendar is open for end date selection