Calendar.dates(byMatching: ...) does not respect repeatedTimePolicy when .nanosecond is set

[hristost]

When searching by dates matching date components, the repeatedTimePolicy field is not respected if the nanoseconds field is set. For example, we want to find the date expected which is just after a daylight switch:

let start    = Date(timeIntervalSince1970: 1730535600.0) // 2024-11-02T01:20:00-0700
let expected = Date(timeIntervalSince1970: 1730625600.0) // 2024-11-03T01:20:00-0800
        
var dc = DateComponents()
dc.hour = 1
dc.minute = 20
dc.second = 0
dc.nanosecond = 0
        
var sequenceIterator = gregorian.dates(byMatching: dc, startingAt: start,  matchingPolicy: .strict, repeatedTimePolicy: .last).makeIterator()
let result = sequenceIterator.next()
assert(result == expected)

when nanosecond is set to a value, enumeration always returns the 01:20 before the switch and the assertion fails.

The bug occurs in Calendar.dateAfterMatchingNanosecond(...) in Calendar_Enumerate.swift. This method simply returns a new date using Calendar.date(from: DateComponents), but in the test above there are two dates matching the components, and we need a way to specify if we want the first or second one.

[hristost]

rdar://124640028