Build/Test: Update dependencies for 5.0

Updates package dependencies to more modern versions, also adds .nvmrc and package-lock.json as followups to [43683] and [43571].

Merge notes: trunk already had an identical .nvmrc. package-lock.json exists in trunk, but has some changes based on the dependency updates.

Props jorbin.
Merges [43684], [43685] and [43686] to trunk.
See #44600.
Fixes #45064.

Built from https://develop.svn.wordpress.org/trunk@43977


git-svn-id: https://core.svn.wordpress.org/trunk@43809 1a063a9b-81f0-0310-95a4-ce76da25c4cd