Install entire node project when creating node_modules digest, subset in sandboxes

[tobni]

Is your feature request related to a problem? Please describe.
Currently, node_modules installations are crafted from installing the "owning" workspace, and all its deps seperately, followed by a digest merge.

This is problematic, especially considering #19235.
Even more so is the fact that the total runtime of pants not benefit from the "incremental" approach, as node_modules is resolved at the project level by the package manager, not per workspace.

Describe the solution you'd like
Install entire project once.

Describe alternatives you've considered

Additional context