Render centerline of runways

[dktue]

Render a dashed line on an aeroway=runway if centerline is set to yes.

Example:

[imagico]

Rendering a centerline signature on aeroway=runway has been considered already - and was part of the two concrete attempts at re-designing runway rendering we had so far (#4346, #4607).

Interpreting centerline=yes for that purpose is currently not viable - the tag is not well established, 69 uses so far, all in Canada, plus the bulk edits you have made today, no documentation.