refactory to move trim/apply default into schema.go (#33754)

* refactory to move trim/apply default into schema.go

* fix comments

* move schema test outside of load folder

pkg/schema/load/testdata/artifacts/dashboards/basic.json

@@ -0,0 +1,153 @@
+{
+  "__inputs": [
+    {
+      "name": "DS_GDEV-TESTDATA",
+      "label": "gdev-testdata",
+      "description": "",
+      "type": "datasource",
+      "pluginId": "testdata",
+      "pluginName": "TestData DB"
+    }
+  ],
+  "__requires": [
+    {
+      "type": "grafana",
+      "id": "grafana",
+      "name": "Grafana",
+      "version": "7.5.0-pre"
+    },
+    {
+      "type": "panel",
+      "id": "table",
+      "name": "Table",
+      "version": ""
+    },
+    {
+      "type": "datasource",
+      "id": "testdata",
+      "name": "TestData DB",
+      "version": "1.0.0"
+    }
+  ],
+  "annotations": {
+    "list": [
+      {
+        "builtIn": 1,
+        "datasource": "-- Grafana --",
+        "enable": true,
+        "hide": true,
+        "iconColor": "rgba(0, 211, 255, 1)",
+        "name": "Annotations & Alerts",
+        "rawQuery": "wtf",
+        "showIn": 0,
+        "type": "dashboard"
+      }
+    ]
+  },
+  "editable": true,
+  "graphTooltip": 0,
+  "id": 42,
+  "links": [],
+  "panels": [
+    {
+      "datasource": "${DS_GDEV-TESTDATA}",
+      "fieldConfig": {
+        "defaults": {
+          "custom": {
+            "align": "right",
+            "filterable": false
+          },
+          "decimals": 3,
+          "mappings": [],
+          "unit": "watt"
+        },
+        "overrides": [
+          {
+            "matcher": {
+              "id": "byName",
+              "options": "Max"
+            },
+            "properties": [
+              {
+                "id": "custom.displayMode",
+                "value": "lcd-gauge"
+              }
+            ]
+          },
+          {
+            "matcher": {
+              "id": "byName",
+              "options": "A"
+            },
+            "properties": [
+              {
+                "id": "custom.width",
+                "value": 200
+              }
+            ]
+          }
+        ]
+      },
+      "gridPos": {
+        "h": 9,
+        "w": 12,
+        "x": 0,
+        "y": 0
+      },
+      "id": 2,
+      "options": {
+        "showHeader": true,
+        "sortBy": []
+      },
+      "pluginVersion": "7.5.0-pre",
+      "targets": [
+        {
+          "alias": "",
+          "csvWave": {
+            "timeStep": 60,
+            "valuesCSV": "0,0,2,2,1,1"
+          },
+          "lines": 10,
+          "points": [],
+          "pulseWave": {
+            "offCount": 3,
+            "offValue": 1,
+            "onCount": 3,
+            "onValue": 2,
+            "timeStep": 60
+          },
+          "refId": "A",
+          "scenarioId": "random_walk_table",
+          "stream": {
+            "bands": 1,
+            "noise": 2.2,
+            "speed": 250,
+            "spread": 3.5,
+            "type": "signal"
+          },
+          "stringInput": ""
+        }
+      ],
+      "title": "Panel Title",
+      "type": "table",
+      "panelSchema": {
+        "maj": 0,
+        "min": 0
+      }
+    }
+  ],
+  "schemaVersion": 27,
+  "style": "dark",
+  "tags": [],
+  "templating": {
+    "list": []
+  },
+  "time": {
+    "from": "now-6h",
+    "to": "now"
+  },
+  "timezone": "browser",
+  "title": "with table",
+  "uid": "emal8gQMz",
+  "version": 2
+}