Restrict GetNamedTimeZoneOffsetNanoseconds return value to less than 24 hours

[anba]

GetNamedTimeZoneOffsetNanoseconds should specify that the absolute value of the returned integer is less than nsPerDay (8.64 × 10¹³).

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This came up during review of the Temporal patches for SpiderMonkey.

[michaelficarra]

Can you explain why a time zone offset can't have a magnitude of 24 hours or more?

[anba]

This is necessary for compatibility with Temporal (for example tc39/proposal-temporal#2260) and if offsets exceed 24 hours, it's also no longer possible to parse string representations of the offset through UTCOffset, because Hour only goes up to 23.