Reimport 1x1 textures as 4x4

[joseph-kaile]

The tile sets are black in 5.3 iOS for some unknown reason. Resizing the 1x1 textures to 4x4 textures makes the issue go away.

[j9liu]

Just a driveby comment -- probably should rename this to transparent4x4 since it is no longer 1x1 :)

[csciguy8]

Fix seems to relate to
#1391

... although nothing in the Unreal docs explicitly say that 1x1 textures are to be avoided...
https://docs.unrealengine.com/4.27/en-US/RenderingAndGraphics/Textures/SupportAndSettings/

[azrogers]

Reverted my code changes, it's a lot easier to just get this in with just the asset changes than to rename the assets, rename their usage in the code, make sure other assets still point to it correctly, etc... and I don't think the name transparent1x1 is really going to cause that much confusion.