[test] Moved all error related toolchains under their own user

This allows to have a cleaner content and a dedicated place for
error related tests.

beat/core/test/prefix/toolchains/errors/double/1.json

+{
+  "connections": [
+    {
+      "to": "echo1.in",
+      "from": "set.out",
+      "channel": "set"
+    },
+    {
+      "to": "echo2.in",
+      "from": "echo1.out",
+      "channel": "set"
+    },
+    {
+      "to": "analysis.in",
+      "from": "echo2.out",
+      "channel": "set"
+    }
+  ],
+  "analyzers": [
+    {
+      "inputs": [
+        "in"
+      ],
+      "synchronized_channel": "set",
+      "name": "analysis"
+    }
+  ],
+  "datasets": [
+    {
+      "outputs": [
+        "out"
+      ],
+      "name": "set"
+    }
+  ],
+  "blocks": [
+    {
+      "inputs": [
+        "in"
+      ],
+      "synchronized_channel": "set",
+      "name": "echo1",
+      "outputs": [
+        "out"
+      ]
+    },
+    {
+      "inputs": [
+        "in"
+      ],
+      "synchronized_channel": "set",
+      "name": "echo2",
+      "outputs": [
+        "out"
+      ]
+    }
+  ],
+  "representation": {
+    "connections": {
+      "set.out/echo1.in": [
+        {
+          "col": 4,
+          "row": 2
+        },
+        {
+          "col": 5,
+          "row": 2
+        },
+        {
+          "col": 6,
+          "row": 2
+        },
+        {
+          "col": 7,
+          "row": 2
+        }
+      ],
+      "echo2.out/analysis.in": [
+        {
+          "col": 22,
+          "row": 2
+        },
+        {
+          "col": 23,
+          "row": 2
+        },
+        {
+          "col": 24,
+          "row": 2
+        },
+        {
+          "col": 25,
+          "row": 2
+        }
+      ],
+      "echo1.out/echo2.in": [
+        {
+          "col": 13,
+          "row": 2
+        },
+        {
+          "col": 14,
+          "row": 2
+        },
+        {
+          "col": 15,
+          "row": 2
+        },
+        {
+          "col": 16,
+          "row": 2
+        }
+      ]
+    },
+    "blocks": {
+      "set": {
+        "width": 5,
+        "height": 3,
+        "col": -1,
+        "row": 0
+      },
+      "analysis": {
+        "width": 6,
+        "height": 3,
+        "col": 25,
+        "row": 0
+      },
+      "echo2": {
+        "width": 6,
+        "height": 3,
+        "col": 16,
+        "row": 0
+      },
+      "echo1": {
+        "width": 6,
+        "height": 3,
+        "col": 7,
+        "row": 0
+      }
+    },
+    "channel_colors": {
+      "set": "#0000FF"
+    }
+  }
+}