[tz] Add new timezone for Hanoi Capital, Vietnam

These are the reasons that I think are reasonable - After merging with Ha Tay, Hanoi (capital) is the largest province in Vietnam - +7:00 (North Vietnam and All Vietnam since 1975) timezone has been the longest unified timezone ever, compared to Asia/Saigon, Asia/Ho_Chi_Minh (modified many times) I would like to suggest adding a timezone for Hanoi or changing the name from Asia/Ho_Chi_Minh to Asia/Hanoi as the official timezone for Vietnam. Having the same article should be considered https://tz.iana.narkive.com/foJrvdQn/tz-patch-tzdata-asia-ha-noi-add-new-tim...