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.

---------

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

games/devtest/mods/testtools/particles.lua

@@ -1,14 +1,27 @@
+local function spawn_clip_test_particle(pos)
+	core.add_particle({
+		pos = pos,
+		size = 5,
+		expirationtime = 10,
+		texture = {
+			name = "testtools_particle_clip.png",
+			blend = "clip",
+		},
+	})
+end
+
 core.register_tool("testtools:particle_spawner", {
-	description = "Particle Spawner".."\n"..
+	description = table.concat({
+		"Particle Spawner",
 		"Punch: Spawn random test particle",
+		"Place: Spawn clip test particle",
+	}, "\n"),
 	inventory_image = "testtools_particle_spawner.png",
 	groups = { testtool = 1, disable_repair = 1 },
 	on_use = function(itemstack, user, pointed_thing)
 		local pos = core.get_pointed_thing_position(pointed_thing, true)
 		if pos == nil then
-			if user then
-				pos = user:get_pos()
-			end
+			pos = assert(user):get_pos()
 		end
 		pos = vector.add(pos, {x=0, y=0.5, z=0})
 		local tex, anim
@@ -32,5 +45,12 @@ core.register_tool("testtools:particle_spawner", {
 			glow = math.random(0, 5),
 		})
 	end,
+	on_place = function(itemstack, user, pointed_thing)
+		local pos = assert(core.get_pointed_thing_position(pointed_thing, true))
+		spawn_clip_test_particle(pos)
+	end,
+	on_secondary_use = function(_, user)
+		spawn_clip_test_particle(assert(user):get_pos())
+	end,
 })