Options to perform common steps after nvs add

[jasongin]

When adding a version, users commonly want to use it immediately, and/or migrate global modules from some existing version to the added version. So it might be convenient if a command syntax something like the following was supported:

nvs add 6.9.1 --use --migrate 6.8.0

That would be just a little shorter than the currently-supported equivalent:

nvs add 6.9.1; nvs use 6.9.1; nvs migrate 6.8.0

Since it's not really a huge difference, I think this is a fairly low priority feature. And personally I sort of prefer to keep the commands simple and discrete... but I'm open to feedback on this.