Ask if amenity=car_sharing is still there

[catdogmat]

It has been briefly mentioned in the original "is it still there" issue (#2074) but hasn't been implemented or discussed any further.

I've just opened a few notes for car sharing stations which are probably gone. Would be useful to add this imo.

Originally posted by @dreua in #2074 (comment)
This PR fixes #5399

[dreua]

Ha, I had no idea it would be that simple!

[matkoniecz]

not really familiar with such places but it seems reasonable?

[westnordost]

But why check every 4 years? I think it should be moved to line 68.

[catdogmat]

But why check every 4 years? I think it should be moved to line 68.

They come and go quite alot where I live, as not many people use them.

[westnordost]

Well, fair enough. I was thinking that this is the same class of things as e.g. a taxi stand or a motorcycle parking, which is in the 6-year category. But, let's not count peas.

[matkoniecz]

(also, it is possible to look at how people answered "is it still there" quests, look how old objects were at time of quest and tweak quest configuration based on that, I did it with some cases)