eng: move selfhost test provider as a workspace extension (#208699)

Testing #208184, closes #207756

.vscode/extensions/vscode-selfhost-test-provider/package.json

@@ -0,0 +1,78 @@
+{
+  "name": "vscode-selfhost-test-provider",
+  "displayName": "VS Code Selfhost Test Provider",
+  "description": "Test provider for the VS Code project",
+  "enabledApiProposals": [
+    "testObserver"
+  ],
+  "engines": {
+    "vscode": "^1.88.0"
+  },
+  "contributes": {
+    "commands": [
+      {
+        "command": "selfhost-test-provider.updateSnapshot",
+        "title": "Update Snapshot",
+        "icon": "$(merge)"
+      }
+    ],
+    "menus": {
+      "commandPalette": [
+        {
+          "command": "selfhost-test-provider.updateSnapshot",
+          "when": "false"
+        }
+      ],
+      "testing/message/context": [
+        {
+          "command": "selfhost-test-provider.updateSnapshot",
+          "group": "inline@1",
+          "when": "testMessage == isSelfhostSnapshotMessage && !testResultOutdated"
+        }
+      ],
+      "testing/message/content": [
+        {
+          "command": "selfhost-test-provider.updateSnapshot",
+          "when": "testMessage == isSelfhostSnapshotMessage && !testResultOutdated"
+        }
+      ]
+    }
+  },
+  "icon": "icon.png",
+  "version": "0.4.0",
+  "publisher": "ms-vscode",
+  "categories": [
+    "Other"
+  ],
+  "activationEvents": [
+    "workspaceContains:src/vs/loader.js"
+  ],
+  "workspaceTrust": {
+    "request": "onDemand",
+    "description": "Trust is required to execute tests in the workspace."
+  },
+  "main": "./out/extension.js",
+  "prettier": {
+    "printWidth": 100,
+    "singleQuote": true,
+    "tabWidth": 2,
+    "arrowParens": "avoid"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/microsoft/vscode.git"
+  },
+  "license": "MIT",
+  "scripts": {
+    "compile": "gulp compile-extension:vscode-selfhost-test-provider",
+    "watch": "gulp watch-extension:vscode-selfhost-test-provider"
+  },
+  "devDependencies": {
+    "@types/node": "18.x"
+  },
+  "dependencies": {
+    "@jridgewell/trace-mapping": "^0.3.25",
+    "ansi-styles": "^5.2.0",
+    "istanbul-to-vscode": "^2.0.1"
+  }
+}