Scala3doc: DRI clash possible between properties and nested classlikes

[Kordyjan]

See the commented out test: https://github.com/lampepfl/dotty/blob/1ba60fafcec2190d7e5e99b0775a26e4b0e54002/scala3doc-testcases/src/tests/functionDRI.scala#L20-L22

Right now val b and trait b would have the same DRI which can end in links inside of documentation not working properly.