[FEATURE] Use validate-npm-package-name to validate package names

[iarna]

Let's get this logic centralized. This'd replace ensureValidName. Things that use fixNameField to validate names should probably be updated to use validate-npm-package-name directly too. cough npm-registry-client cough

[othiym23]

We should definitely do this!

cough npm-registry-client cough

📝 an issue plzthxomgbbq!

[iarna]

I'd like to see npm/validate-npm-package-name#1 addressed before we do the npm-registry-client changes, as I'd prefer to not change its semantics.

[zeke]

An attempt is here: npm/validate-npm-package-name#2