Some vendored crates get absolute paths in `MODULE.bazel.lock`

In my `Cargo.toml`, I have:

```
[workspace.dependencies]
...
flatbuffers-tonic = { path = "third_party/flatbuffers-tonic/flatbuffers-tonic" }
flatbuffers-tonic-build = { path = "third_party/flatbuffers-tonic/flatbuffers-tonic-build" }
flatbuffers-util = { path = "third_party/flatbuffers-tonic/flatbuffers-util" }
...
```

When these crates find their way into `MODULE.bazel.lock`, they are prefixed with absolute paths. This brakes cross-machine and cross-platform builds of these crates.

Start with the workspace dependency entries in Cargo.toml and reproduce generation of MODULE.bazel.lock using the vendored crate paths shown. Trace where those paths are written into the lockfile; done means the lockfile uses portable paths and builds work across machines and platforms.

Written by the indexing model from the issue text.