Support partial namespace import

[innocenzi]

I would like to suggest implementing a quick action to allow importing a namespace based on this syntax:

Json\encode($value);

When looking up quick actions on encode here, Intelephense would suggest importing the proper namespace as follows:

use Tempest\Support\Json;

Json\encode($value);

This pattern is common in codebases with utilities, eg. https://github.com/azjezz/psl.