Framework functions receive arguments boxed twice in an Array

I'm not sure this is intentional or not, but I don't see the reason for the arguments to be boxed twice in an array when reaching the main process of a framework plugin/element. That is:
- `cordova.exec` transfers the array of argument to `_cdvElectronIpc`, which in turns send the array to the main process
- the `cdv-plugin-exec` handler uses vararg for the last argument, which basically boxes the argument into another array
- the framework function receives a single argument, which is then an array or arrays

Is this intentional?

Trace the argument flow from cordova.exec through _cdvElectronIpc and the cdv-plugin-exec handler to the framework function. First determine whether the second array boxing is intentional; done means the expected argument shape and any required behavior change are explicitly established.

Written by the indexing model from the issue text.