Surface synonyms, remove concrete:plates as selectable surface

[westnordost]

fixes #6265

Turned out to be more involved.

Because previously, we didn't have the notion of aliases for surfaces (e.g. surface=earth == surface=dirt) like we had for building types.

This would lead to that when one would confirm the shown surface in a re-survey or overlay, let's say paving stones, and it was previously tagged as surface=bricks (considered an alias/subtype of this), then it would be re-tagged as surface=paving_stones. But we don't want that, we want it to stay bricks in this case.

So, I made this work like the aliases for BuildingType, and also made it consistent how both of these are implemented.

[westnordost]

@matkoniecz a review by you would be highly appreciated, as you've been the person most involved with surface stuff

[aikencz]

I strongly disagree with removing of concrete:plates. I used this surface type relatively often (and correctly!). With the new version, it brings additional work to me. I have to add a note in StreetComplete and then set the correct surface in iD or JOSM.

[westnordost]

Well, see here for my final opinion on it and why I agreed to remove it in the end:
#6265 (comment)