Increased fractional precision in Duration strings

[ptomato]

(Moved from tc39/proposal-temporal#1712)

Temporal.Duration strings are currently allowed to specify fractional hours, minutes, and seconds, up to 9 digits.

Advantages:

Example strings that are currently rejected by Temporal.Duration.from(), that nonetheless represent exact numbers of nanoseconds:

• PT0.00000000001H → 36 nanoseconds
• PT0.0000000001M → 6 nanoseconds

Concerns:

Increasing the allowed precision beyond 9 digits for fractional seconds, 10 digits for fractional minutes, or 11 digits for fractional hours, may pose implementation difficulties since implementations would have to calculate with fractional nanoseconds.

Prior art:

• TBD

Constraints / corner cases:

• TBD