Introduce this_week?, this_month?, and this_year? to Date/Time

[MatheusRich]

Similar to today?, tomorrow?, and yesterday?, these methods are useful to
query time instances against the current period.

unless some_date.in_this_week?
  link_to "See week recap", week_recap_path(some_date)
end

Checklist

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• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
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[MatheusRich]

I thought comparing as date made sense for these units. Unless we plan to add current_hour? too, which then it would be best to convert to_time instead.

[p8]

A comment about a similar PR to add methods like yesterday? probably applies here as well:

New Active Support core extensions that aren't used internally by Rails are often rejected in favour of being proposed to Ruby directly, but since these complement existing Active Support methods it seems reasonable to consider adding them here. That decision will have to be made by a committer though.

#37625 (comment)

[MatheusRich]

@jeremy @dhh sorry to ping y'all directly, I'd love a thumbs up/down on this. We have simimilar query methods, and I'm assuming you have experience with similar methods because of HEY.

[dhh]

I prefer skipping the aliases. We already use #in_ for conversions, like #in_minutes. But #this_week? matches #today? So I'm good with this without the #in_ aliases 👍

[MatheusRich]

@dhh Done. Thank you!