Adds stair entities (with new sprites,) nukes stair decals (#20279)

* nukes stair decals, adds entity stairs

* FUCK. my furniture

* fix deprecated sprites

Resources/Textures/Structures/stairs.rsi/meta.json

@@ -0,0 +1,18 @@
+{
+    "version": 1,
+    "license": "CC-BY-SA-3.0",
+    "copyright": "Taken from /vg/station at commit https://github.com/vgstation-coders/vgstation13/commit/02b9f6894af4419c9f7e699a22c402b086d8067e",
+    "size": {
+        "x": 32,
+        "y": 32
+    },
+    "states": [
+		{
+			"name": "stairs",
+			"directions": 4
+		},
+        {
+            "name": "stairs_stage"
+        }
+    ]
+}