Bicycle routing should default to dismount access on footways/pedestrian highways, currently excluded

Valhalla currently avoids routing bicycles over `highway=footway` and `highway=pedestrian` unless these ways have tags such as `bicycle=dismount`, `bicycle=yes`, `bicycle=permissive`, etc. The router should assume that pushing a bike is generally legal in most footpaths at walking speed, so these ways would still be somewhat strongly avoided unless when they're useful shortcuts. Only `bicycle=no` should be treated as strict prohibition even for pushing.