add support for deprecated (boundary) multipolygon tagging

[SlowMo24]

TIL that one also could have used enclave/exclave as roles on boundary multipolygons. We should add support for them as well when dealing with old data.

Btw: on a more general note: It might be kind of a good idea to start thinking about how to document changes of OSM's tagging system. There would be different cases: a) stuff that used to be mapped differently – for example with another tag – in the past, like highway=ford is now ford=yes, b) stuff that used to be mapped more coarsly and has got an improved tagging scheme (e.g. some of the power stuff).

see https://gitlab.gistools.geog.uni-heidelberg.de/giscience/big-data/ohsome/oshdb/issues/46

[Hagellach37]

This is out of scope for OSHDB (for now), but could be added to the tag interpreter.