date: Validate nanoseconds range and normalize negative zero duration

[adapik]

Follow-up to #23629 and #23759.

// 1. Previously accepted: nanoseconds is 4294967301 (2^32 + 5), but the
//    internal value is 5, so it compares equal to a 5ns duration.
unserialize('O:13:"Time\Duration":3:{s:7:"seconds";i:0;s:11:"nanoseconds";i:4294967301;s:8:"negative";b:0;}');
// Now: Exception: Invalid serialization data for Time\Duration object

// 2. Previously ->negative stayed true and serialize() round-tripped b:1.
$d = unserialize('O:13:"Time\Duration":3:{s:7:"seconds";i:0;s:11:"nanoseconds";i:0;s:8:"negative";b:1;}');
var_dump($d->negative); // Now: bool(false), like Duration::fromSeconds(0)->negate()

[TimWolla]

Good catch, thank you! I have some remarks regarding the actual implementation.

[adapik]

Both comments addressed