[engsys] update devcontainer.json (#26793)

Move "settings" and "extensions" inside `customizations/vscode` as
suggested at https://containers.dev/supporting

Author: jeremymeng

.devcontainer/devcontainer.json

@@ -1,29 +1,5 @@
 {
   "name": "GitHub Codespaces (Default)",
-  "settings": {
-    "terminal.integrated.shell.linux": "/bin/bash",
-    "go.useGoProxyToCheckForToolUpdates": false,
-    "go.useLanguageServer": true,
-    "go.gopath": "/go",
-    "go.goroot": "/usr/local/go",
-    "go.toolsGopath": "/go/bin",
-    "python.pythonPath": "/opt/python/latest/bin/python",
-    "python.linting.enabled": true,
-    "python.linting.pylintEnabled": true,
-    "python.formatting.autopep8Path": "/usr/local/py-utils/bin/autopep8",
-    "python.formatting.blackPath": "/usr/local/py-utils/bin/black",
-    "python.formatting.yapfPath": "/usr/local/py-utils/bin/yapf",
-    "python.linting.banditPath": "/usr/local/py-utils/bin/bandit",
-    "python.linting.flake8Path": "/usr/local/py-utils/bin/flake8",
-    "python.linting.mypyPath": "/usr/local/py-utils/bin/mypy",
-    "python.linting.pycodestylePath": "/usr/local/py-utils/bin/pycodestyle",
-    "python.linting.pydocstylePath": "/usr/local/py-utils/bin/pydocstyle",
-    "python.linting.pylintPath": "/usr/local/py-utils/bin/pylint",
-    "lldb.executable": "/usr/bin/lldb",
-    "files.watcherExclude": {
-      "**/target/**": true
-    }
-  },
   "remoteUser": "codespace",
   "overrideCommand": false,
   "workspaceMount": "source=${localWorkspaceFolder},target=/home/codespace/workspace,type=bind,consistency=cached",
@@ -37,12 +13,6 @@
     "seccomp=unconfined",
     "--privileged"
   ],
-  // Add the IDs of extensions you want installed when the container is created.
-  "extensions": [
-    "GitHub.vscode-pull-request-github",
-    "MS-vsliveshare.vsliveshare",
-    "VisualStudioExptTeam.vscodeintellicode"
-  ],
   "postCreateCommand": "bash .devcontainer/init.sh",
   // Use 'forwardPorts' to make a list of ports inside the container available locally.
   // "forwardPorts": [],
@@ -55,6 +25,38 @@
           }
         }
       }
+    },
+    "vscode": {
+      "settings": {
+        "terminal.integrated.shell.linux": "/bin/bash",
+        "go.useGoProxyToCheckForToolUpdates": false,
+        "go.useLanguageServer": true,
+        "go.gopath": "/go",
+        "go.goroot": "/usr/local/go",
+        "go.toolsGopath": "/go/bin",
+        "python.pythonPath": "/opt/python/latest/bin/python",
+        "python.linting.enabled": true,
+        "python.linting.pylintEnabled": true,
+        "python.formatting.autopep8Path": "/usr/local/py-utils/bin/autopep8",
+        "python.formatting.blackPath": "/usr/local/py-utils/bin/black",
+        "python.formatting.yapfPath": "/usr/local/py-utils/bin/yapf",
+        "python.linting.banditPath": "/usr/local/py-utils/bin/bandit",
+        "python.linting.flake8Path": "/usr/local/py-utils/bin/flake8",
+        "python.linting.mypyPath": "/usr/local/py-utils/bin/mypy",
+        "python.linting.pycodestylePath": "/usr/local/py-utils/bin/pycodestyle",
+        "python.linting.pydocstylePath": "/usr/local/py-utils/bin/pydocstyle",
+        "python.linting.pylintPath": "/usr/local/py-utils/bin/pylint",
+        "lldb.executable": "/usr/bin/lldb",
+        "files.watcherExclude": {
+          "**/target/**": true
+        }
+      },
+      // Add the IDs of extensions you want installed when the container is created.
+      "extensions": [
+        "GitHub.vscode-pull-request-github",
+        "MS-vsliveshare.vsliveshare",
+        "VisualStudioExptTeam.vscodeintellicode"
+      ]
     }
   }
 }