cargo: Meson is not able to automatically handle path dependencies in workspaces

**Describe the bug**
Take two crates in a workspace, `foo` and `bar`. `foo` depends on `bar` through a path dependency. During setup, Meson isn't able to make the path dep a subproject, and the setup fails. However, Cargo is able to build the project.

**To Reproduce**
See the minimal reproducer attached.

[meson-cargo-path-dep-reproducer.zip](https://github.com/user-attachments/files/31346396/meson-cargo-path-dep-reproducer.zip)

**Expected behavior**
Meson should be able to build the library

**system parameters**
* Native build
* Linux (GNOME OS)
* Python 3.14.7
* Meson version: master

Start with the attached minimal reproducer and trace Meson's Cargo setup handling for a workspace path dependency. Compare the failing setup with Cargo's successful build behavior, then verify that Meson can configure and build the library from the reproducer.

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