[ui5-daterange-picker] Timezone issue - firstDateValue and lastDateValue attributes are wrong

[Neeeko]

I'm part of the SuccessFactors team

Describe the bug
Following my previous issue: #2182
The UI of the ui5-daterange-picker now works properly and display the correct value (0.23.2).
However, on the same timezone as the previous issue, the firstDateValue and lastDateValue contains wrong Dates.

For example: selecting Sep 1, 2020 - Sep 30, 2020 =>
firstDateValue = Sun Aug 30 2020 16:00:00 GMT-0800 (Alaska Daylight Time)
lastDateValue = Mon Sep 28 2020 16:00:00 GMT-0800 (Alaska Daylight Time)

while it would probably make more sense to have something like:
firstDateValue = Tue Sep 1 2020 00:00:00 GMT-0800 (Alaska Daylight Time)
lastDateValue = Wed Sep 30 2020 00:00:00 GMT-0800 (Alaska Daylight Time)

To reproduce
Steps to reproduce the behavior:

1. Change your computer timezone to a timezone in the US West Coast (for example in Anchorage, Alaska). (Using a Mac, go to Preferences => Date and Time => Time zone.
2. Go to https://codesandbox.io/s/tender-shtern-85xgu?file=/src/App.js and select dates in the DateRangePicker
3. The dates are wrong.

Expected behavior
DateRangePicker should be timezone agnostic. The dates that are displayed in the ui5-daterange-picker and the dates in firstDateValue and lastDateValue should be identical.

Screenshots

Context

• UI5 Web Components version: 0.23.2
• OS/Platform: macOS Catalina

Affected components ui5-daterange-picker