time: add week_of_year()

[kbkpbot]

Follow ISO 8601 standard.
Fix issue #23835

[huly-for-github]

Connected to Huly®: V_0.6-22243

[spytheman]

I tried the following program:

import time

mut now := time.now()
for d in 1..315 {
    println('>> ${now} | d: ${d:03} | .day_of_week(): ${now.day_of_week()} |  .strftime_V: ${now.strftime('%V')} | .week_of_year: ${now.week_of_year():02}')
    now = now.add_days(1)
}

which printed:

Is there a reason for the difference from the .strftime('%V') result, around the new year?

>> 2025-12-28 23:57:53 | d: 303 | .day_of_week(): 7 |  .strftime_V: 52 | .week_of_year: 52
>> 2025-12-29 23:57:53 | d: 304 | .day_of_week(): 1 |  .strftime_V: 01 | .week_of_year: 53
>> 2025-12-30 23:57:53 | d: 305 | .day_of_week(): 2 |  .strftime_V: 01 | .week_of_year: 53
>> 2025-12-31 23:57:53 | d: 306 | .day_of_week(): 3 |  .strftime_V: 01 | .week_of_year: 53
>> 2026-01-01 23:57:53 | d: 307 | .day_of_week(): 4 |  .strftime_V: 01 | .week_of_year: 01

[spytheman]

Excellent work.
Thanks for the new function 🙇🏻‍♂️ .

I've tried to implement it in the past for .github/workflows/show_manual_release_cmd.vsh, but could not figure out the full details, so I settled on using .strftime() instead.