Mk/Uses/electron.mk: Improve automatic npm version detection

The framework assumed the name and the version of a node package
manager is specified as the key "packageManager" [1] in package.json
like:
{

"packageManager": "<name>@<version>+<hash>"

}

However, the name and the version can be also specified using the key
"devEngines.packageManager" [1] like:
{

"devEngines":{
  "packageManager": {
    "name": "<name>",
    "version": "<version>+<hash>"
  }
}

}

This change enables automatic npm version detection for the both
cases.

[1] https://github.com/nodejs/corepack/blob/main/README.md#when-authoring-packages