Include pre-release versions in uv python install --reinstall (#13645)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->
This change allows for `uv python install --reinstall` to include
pre-releases when reinstalling. It does this by explicitly allowing
pre-releases to be included within `PythonRequest::Any` if the user does
not specify a version to reinstall.

Fixes #13582

## Test Plan

<!-- How was it tested? -->
```bash
uv python install 3.14 3.13 3.10
uv python install --no-config --reinstall
```

crates/uv-python/src/downloads.rs

@@ -204,7 +204,11 @@ impl PythonDownloadRequest {
                     .with_version(version.clone()),
             ),
             PythonRequest::Key(request) => Some(request.clone()),
-            PythonRequest::Default | PythonRequest::Any => Some(Self::default()),
+            PythonRequest::Any => Some(Self {
+                prereleases: Some(true), // Explicitly allow pre-releases for PythonRequest::Any
+                ..Self::default()
+            }),
+            PythonRequest::Default => Some(Self::default()),
             // We can't download a managed installation for these request kinds
             PythonRequest::Directory(_)
             | PythonRequest::ExecutableName(_)