Add particle blend mode "clip" (#15444)

This lets modders avoid alpha blending rendering bugs as well as potential (future) performance issues.
The appropriate blend modes are also used for node dig particles.

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Co-authored-by: sfan5 <sfan5@live.de>

src/particles.h

@@ -233,7 +233,8 @@ namespace ParticleParamTypes
 	}
 
 	enum class AttractorKind : u8 { none, point, line, plane };
-	enum class BlendMode     : u8 { alpha, add, sub, screen  };
+	// Note: Allows at most 8 enum members (due to how this is serialized)
+	enum class BlendMode     : u8 { alpha, add, sub, screen, clip, BlendMode_END };
 
 	// these are consistently-named convenience aliases to make code more readable without `using ParticleParamTypes` declarations
 	using v3fRange = RangedParameter<v3fParameter>;