This introduces a compound boolean EncodedValue bus_access including the oneway handling but without road_class handling ("bus" in the sense of a psv = public service vehicle).

A separate bus_oneway_access is unnecessary as the only known use case atm (for ambulances) would be to allow opposite travel of oneways which could be achieved with backward_bus_access instead.

This is a replacement of #2710. The new ModeAccessParser can be used with any of the values in the TransportationMode enum e.g. also motorcycle. The idea is that is can be (later) used as a replacement for CarAccessParser too. (Furthermore the oneway code in CarAccessParser should be simplified)

Unfortunately the enum in #2710 cannot handle oneway roads properly. For #2710 there is a problem: if bus=yes on oneway roads and motor_vehicle=no then the bus profile would allow access in the opposite direction of the oneway road too. See this route as an example. (We could make the enum direction-dependent to handle oneway roads. Then we could also consider tags like "bus=designated" in the profile to prefer these ways. But this would be too confusing as the enum would no longer represent the OSM data and bus==YES in the custom_model would not necessarily mean bus=yes in OSM.)

The usage is outlined in the bus.json.