Add px suffix for TileSet separation property

[philippesic]

Add px suffix to TileMap > TileSet > Selection > Seperation. Visual change.

Fixes #80869

[AThousandShips]

You have several unrelated changes in your PR, please squash your commits into one, see here

[AThousandShips]

Minus the cleaning of the commit history this looks good

[dalexeev]

#80869 (comment):

TileSet->Select is this Animation Separation "px" too? idk
I tried setting up animation separation and got a not enough room error, so maybe not "px". idk

godot/editor/plugins/tiles/tile_set_atlas_source_editor.cpp

Line 428 in 6758a7f

p_list->push_back(PropertyInfo(Variant::VECTOR2I, PNAME("animation_separation")));

godot/scene/resources/tile_set.cpp

Line 4086 in 6758a7f

property_info = PropertyInfo(Variant::INT, "animation_separation", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR);

[philippesic]

Squashed unrelated commits

[YuriSizov]

Could you please amend your commit message? We don't use the "fix", "chore", etc prefixes as per the project's preferred style. Just dropping it would be fine.

TileSet->Select is this Animation Separation "px" too? idk

Documentation says it's in "grid tiles".

[YuriSizov]

Thanks! And congrats on your first merged Godot PR!