Support rotate90 in Defold export plugins #3369

Defold has added support for 90-degree rotation on tilemaps. Tiled ships with two Defold export plugins, defold and defoldcollection, which should now support this new feature as well.

Since Tiled implements tile rotation through a diagonal flip, the diagonal flip needs to be mapped to Defold's rotate90 flag along with an affect on the v_flip or h_flip flags, depending on the order of the clockwise 90-degree rotation and the flip.

Reported in comment on itch.io.