[Bug] intl.parseDate fails when microsecond fractions round up to a full second

[filipKovachev]

intl.parseDate fails to parse valid ISO-8601 datetime strings when the fractional seconds are close enough to 1 second to round to 1000ms. The issue appears to be caused by the fractional part .999978 being converted to 999.978ms and rounded to 1000ms, which is outside the valid range and causes the parser to return null. This affects zoned datetime strings with microsecond precision:

https://stackblitz.com/edit/react-yfyvwquq-8vlgamx2?file=app%2Fapp.tsx

Reported in Ticket ID: 1705498