Isometric tileset changes for 3d vision

[Rewryte]

Summary

Tileset changes for CleverRaven/Cataclysm-DDA#66383

Content of the change

Basically the isometric counterpart of #2008.
This should only be merged if CleverRaven/Cataclysm-DDA#66383 is.

Isometric tilesets require minor changes as follows:

• t_open_air and variants should either be unassigned or semi-transparent. I opted to unassign them and let the fallback fog do the job. Feel free to replace it if there is something better.
• tr_ledge needs to be assigned a blank sprite to prevent a fallback sprite from being drawn.

Affected tilesets are SmashButton_iso and Ultica_iso.
My sprites are made in Krita 5.1 and saved using default settings.

Testing

Compose script ran successfully and modified tiles interact properly with the 3D vision PR. Did not notice any unintended changes in comparison to the current master.

Additional information

[Fris0uman]

hitbutton is missing a t_open_air sprite here, no?

[Rewryte]

hitbutton is missing a t_open_air sprite here, no?

Well, you're not wrong. The 3D vision PR includes changes to the fallback system when sprites are not found. A missing t_open_air will cause fog to be drawn in its place.

[Fris0uman]

You're removng the json that assigns 687_t_open_air_0 to t_open_air, you could instead edit 687_t_open_air_0 to be the fog and rename it t_open_air

[Rewryte]

Yeah, I guess I could. It wouldn't be exactly the same, but after trying it out it did not turn out as bad as I thought it would. Main difference is that the fog is drawn a bit higher than the code would have done.