setAttrByPath should take a set as an argument

[Shou]

Issue description

setAttrByPath currently takes two arguments, the key and the value, and returns a new set where the given key is set to the given value. While setAttr takes a set, key, and value, but does not allow for full paths like implied by the name of the function at hand. I think it would fit better into the attrsets module by taking a set as an argument as well so setAttrByPath : Set -> [String] -> a -> Set. setAttr can then be defined in terms of setAttrByPath, and we can also add a new function that covers the old behaviour, also defined in terms of setAttrByPath.

[stale]

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