Remove DanTup.tiler

I haven't been maintaining this package for a while (besides updating tests). Often subtle (acceptable) changes to the golden files cause a break that requires updating multiple repositories (tests, Tiler, Tiler-test-maps) to unblock rolls.

Maintaining these tests is probably not a good trade-off given they're really only testing things that Flutter should already be testing (rendering some images and shapes to a canvas).

See flutter#376