Stabilize Python upgrades (#17766)

Includes a few things...

- Drops preview warnings for use of `uv python upgrade` and `uv python
install --upgrade`
- Adds `--resolve-links` to `uv python find`, which I needed in test
cases to retain existing snapshots
- Fixes issues in our "Using environment ..." messages on Windows which
were incorrect
- Refactors `from_executable` for the `PythonMinorVersionLink` type
(https://github.com/astral-sh/uv/pull/17842/commits/28b2ed2525327d94fdf5372a29bbbc476d74680f)
to use the type system to prevent incorrect construction (for above)
- Removes special casing where we only upgrade links if they already
exist, which existed so preview wasn't needed on every invocation
- Fixes a bug with `PythonMinorVersionLink::exists` which returned
`true` even if the link pointed to the wrong Python installation leading
to discovery failures

crates/uv-python/src/installation.rs

@@ -260,7 +260,6 @@ impl PythonInstallation {
             reporter,
             python_install_mirror,
             pypy_install_mirror,
-            preview,
         )
         .await?;
 
@@ -278,7 +277,6 @@ impl PythonInstallation {
         reporter: Option<&dyn Reporter>,
         python_install_mirror: Option<&str>,
         pypy_install_mirror: Option<&str>,
-        preview: Preview,
     ) -> Result<Self, Error> {
         let installations = ManagedPythonInstallations::from_settings(None)?.init()?;
         let installations_dir = installations.root();
@@ -321,7 +319,7 @@ impl PythonInstallation {
             .patch()
             .is_some_and(|p| p >= highest_patch)
         {
-            installed.ensure_minor_version_link(preview)?;
+            installed.ensure_minor_version_link()?;
         }
 
         if let Err(e) = installed.ensure_dylib_patched() {