Improve documentation and usage of release_year

[seproDev]

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Description of your pull request and other information

• Update docs to better reflect actual usage of release_year
• Auto generate release year if not present
• Fix HarpodeonIE, which reported an incorrect release date when only the year was known

Closes #7263

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• Fix or improvement to an extractor (Make sure to add/update tests)
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Copilot Summary

🤖 Generated by Copilot at cfea45e

Summary

📅🎞️🛠️

This pull request adds a new release_year field to the common metadata fields for extracted videos, and updates the Harpodeon extractor to use it. It also adds a logic to infer the release_year from the release_date if possible.

release_year field
added to InfoExtractor
autumn of metadata

Walkthrough

• Add a new common field release_year to the InfoExtractor class and document its meaning and usage (link)
• Remove an outdated documentation line that referred to release_year as an album-specific field (link)
• Update the Harpodeon extractor to use the release_year field instead of the release_date field and convert the year to an integer or None (link, link)
• Update the test cases for the Harpodeon extractor to reflect the change from release_date to release_year and use integers instead of strings (link, link, link)
• Add a logic to the YoutubeDL class to calculate the release_year field from the release_date field if not explicitly set by the extractor (link)

[bashonly]

The thing that gives me pause about this is that it will make so many otherwise-passing download tests now fail

Also could probably just use int() here, but either way is fine

[pukkandan]

We can make an exception in the tester similar to

yt-dlp/test/helper.py

Lines 221 to 223 in 21dc069

	# display_id may be generated from id
	if test_info_dict.get('display_id') == test_info_dict.get('id'):
	test_info_dict.pop('display_id')

[pukkandan]

Suggested change

	if info_dict.get('release_year') is None and info_dict.get('release_date') is not None:
	info_dict['release_year'] = int_or_none(info_dict['release_date'][:4])
	if not info_dict.get('release_year'):
	info_dict['release_year'] = traverse_obj(info_dict, ('release_date', lambda x: int(x[:4])))

[seproDev]

Okay, so should this be used as an exception in sanitize_got_info_dict?

    # release_year may be generated from release_date
    if test_info_dict.get('release_year') and test_info_dict.get('release_date'):
        test_info_dict.pop('release_year')

There shouldn't be that many IE's that return both a release_date and release_year.
I could find: ArchiveOrgIE, MonstercatIE, TrueIDIE (inconstant), and YoutubeIE

[pukkandan]

There can be situations in theory where the year doesn't match the date. I think this'd be better:

    if try_call(lambda: test_info_dict['release_year'] == int(test_info_dict['release_date'][:4])):
        test_info_dict.pop('release_year')

That way only the auto-generated value will be excluded

[pukkandan]

and YoutubeIE

release_year is currently broken for Youtube if I remember right