GeezerVison

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* pythongh-159739: Preserve large years in time conversions

The time module added 1900 to the C library year using int arithmetic, which overflowed for timestamps whose calendar year exceeds INT_MAX. On platforms that accept these timestamps, gmtime(), localtime(), and ctime() could report a negative year; perform the addition in a wider type. Backport to 3.15 and 3.14.

* pythongh-159739: Round-trip large years and validate datetime timestamps

Time tuple consumers parsed calendar years as C int before subtracting 1900, so they rejected valid struct_time results. Date and datetime timestamp conversion could also overflow before reporting the invalid year. Preserve the full time tuple range and report oversized datetime years correctly. Backport to 3.15 and 3.14.
(cherry picked from commit e1a4c15)

Co-authored-by: Jelle Zijlstra <[email protected]>