Rename to uv (#1302)

First, replace all usages in files in-place. I used my editor for this.
If someone wants to add a one-liner that'd be fun.

Then, update directory and file names:

```
# Run twice for nested directories
find . -type d -print0 | xargs -0 rename s/puffin/uv/g
find . -type d -print0 | xargs -0 rename s/puffin/uv/g

# Update files
find . -type f -print0 | xargs -0 rename s/puffin/uv/g
```

Then add all the files again

```
# Add all the files again
git add crates
git add python/uv

# This one needs a force-add
git add -f crates/uv-trampoline
```

crates/uv-resolver/src/python_requirement.rs

@@ -0,0 +1,71 @@
+use distribution_types::{CompatibleDist, Dist};
+use pep440_rs::{Version, VersionSpecifiers};
+use pep508_rs::MarkerEnvironment;
+use uv_interpreter::Interpreter;
+
+#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
+pub struct PythonRequirement {
+    /// The installed version of Python.
+    installed: Version,
+    /// The target version of Python; that is, the version of Python for which we are resolving
+    /// dependencies. This is typically the same as the installed version, but may be different
+    /// when specifying an alternate Python version for the resolution.
+    target: Version,
+}
+
+impl PythonRequirement {
+    pub fn new(interpreter: &Interpreter, markers: &MarkerEnvironment) -> Self {
+        Self {
+            installed: interpreter.python_version().clone(),
+            target: markers.python_full_version.version.clone(),
+        }
+    }
+
+    /// Return the installed version of Python.
+    pub(crate) fn installed(&self) -> &Version {
+        &self.installed
+    }
+
+    /// Return the target version of Python.
+    pub(crate) fn target(&self) -> &Version {
+        &self.target
+    }
+
+    /// If the dist doesn't match the given Python requirement, return the version specifiers.
+    pub(crate) fn validate_dist<'a>(
+        &self,
+        dist: &'a CompatibleDist,
+    ) -> Option<&'a VersionSpecifiers> {
+        // Validate the _installed_ file.
+        let requires_python = dist.for_installation().requires_python.as_ref()?;
+
+        // If the dist doesn't support the target Python version, return the failing version
+        // specifiers.
+        if !requires_python.contains(self.target()) {
+            return Some(requires_python);
+        }
+
+        // If the dist is a source distribution, and doesn't support the installed Python
+        // version, return the failing version specifiers, since we won't be able to build it.
+        if matches!(dist.for_installation().dist, Dist::Source(_)) {
+            if !requires_python.contains(self.installed()) {
+                return Some(requires_python);
+            }
+        }
+
+        // Validate the resolved file.
+        let requires_python = dist.for_resolution().requires_python.as_ref()?;
+
+        // If the dist is a source distribution, and doesn't support the installed Python
+        // version, return the failing version specifiers, since we won't be able to build it.
+        // This isn't strictly necessary, since if `dist.resolve_metadata()` is a source distribution, it
+        // should be the same file as `dist.install_metadata()` (validated above).
+        if matches!(dist.for_resolution().dist, Dist::Source(_)) {
+            if !requires_python.contains(self.installed()) {
+                return Some(requires_python);
+            }
+        }
+
+        None
+    }
+}