Support dependencies into git workspaces

[konstin]

Say we have our local workspace with a package a, and another workspace in a git repository with c and d. We have a -> c, c -> d. Currently, this fails by resolving c to the git repository but d to pypi.

To reproduce:

[project]
name = "a"
version = "0.1.0"
requires-python = ">=3.12"
dependencies = ["c"]

[tool.uv.sources]
c = { git = "https://github.com/konstin/workspace-git-path-dep-test", subdirectory = "packages/c" }

https://github.com/konstin/workspace-git-path-dep-test contains the packages c and d.