build: upgrade to Node.js 20 via NodeSource

Replace apt-based nodejs/npm installation with NodeSource repository
to provide Node.js 20.x for workflow steps.

- Update build/config.json to use script-based installation
- Add install_nodejs-20() function in build/tools.sh using NodeSource

Author: jackluo923

build/config.json

@@ -79,10 +79,9 @@
     },
     {
       "category": "node",
-      "source": "apt",
+      "source": "script",
       "packages": [
-        "nodejs",
-        "npm"
+        "nodejs-20"
       ]
     },
     {

build/tools.sh

@@ -89,6 +89,12 @@ function install_yq() {
   mv "/tmp/yq_linux_${DPKG_ARCH}" /usr/local/bin/yq
 }
 
+function install_nodejs-20() {
+  # Install Node.js 20.x and npm using NodeSource setup script
+  curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
+  apt-get install -y --no-install-recommends nodejs
+}
+
 function install_powershell() {
   local DPKG_ARCH PWSH_VERSION PWSH_DOWNLOAD_URL