Add override namespace to pyproject.toml/uv.toml (#3839)

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## Summary

See #3834 .

This PR adds a new namespace, `override-dependencies`, to
pyproject.toml/uv.toml.
This namespace assumes that the dependencies you want to override are
written in the form of `requirements.txt`.


a example of pyproject.toml
```toml
[project]
name = "example"
version = "0.0.0"
dependencies = [
  "flask==3.0.0"
]

[tool.uv]
override-dependencies = [
  "werkzeug==2.3.0"
]
```

This will improve usability by allowing you to override dependencies
without having to specify the --override option when running `uv pip
compile/install`.

## Test Plan

added test to `crates/uv/tests/pip_compile.rs`.

---------

Co-authored-by: konstin <konstin@mailbox.org>

crates/pep508-rs/src/origin.rs

@@ -9,6 +9,8 @@ pub enum RequirementOrigin {
     File(PathBuf),
     /// The requirement was provided via a local project (e.g., a `pyproject.toml` file).
     Project(PathBuf, PackageName),
+    /// The requirement was provided via a workspace.
+    Workspace,
 }
 
 impl RequirementOrigin {
@@ -17,6 +19,8 @@ impl RequirementOrigin {
         match self {
             RequirementOrigin::File(path) => path.as_path(),
             RequirementOrigin::Project(path, _) => path.as_path(),
+            // Multiple toml are merged and difficult to track files where Requirement is defined. Returns a dummy path instead.
+            RequirementOrigin::Workspace => Path::new("(workspace)"),
         }
     }
 }