Add Go to Definition for unexists labels

[Fil-Den]

This PR implements a new feature that enables the "go to definition" functionality for labels that are not defined within a package. This enhancement is particularly useful when navigating definitions for labels like visibility = ["//path/to/package:__subpackages__"].

[Fil-Den]

@withered-magic, could you please review this PR?

[Fil-Den]

@withered-magic, can you merge this PR?

[withered-magic]

Thanks!