Use ast::PythonVersion internally in the formatter and linter (#16170)

## Summary

This PR updates the formatter and linter to use the `PythonVersion`
struct from the `ruff_python_ast` crate internally. While this doesn't
remove the need for the `linter::PythonVersion` enum, it does remove the
`formatter::PythonVersion` enum and limits the use in the linter to
deserializing from CLI arguments and config files and moves most of the
remaining methods to the `ast::PythonVersion` struct.

## Test Plan

Existing tests, with some inputs and outputs updated to reflect the new
(de)serialization format. I think these are test-specific and shouldn't
affect any external (de)serialization.

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_python_ast/src/lib.rs

@@ -6,6 +6,7 @@ pub use generated::*;
 pub use int::*;
 pub use nodes::*;
 pub use operator_precedence::*;
+pub use python_version::*;
 
 pub mod comparable;
 pub mod docstrings;
@@ -19,7 +20,7 @@ mod node;
 mod nodes;
 pub mod operator_precedence;
 pub mod parenthesize;
-pub mod python_version;
+mod python_version;
 pub mod relocate;
 pub mod script;
 pub mod statement_visitor;

crates/ruff_python_ast/src/python_version.rs

@@ -4,6 +4,7 @@ use std::fmt;
 ///
 /// N.B. This does not necessarily represent a Python version that we actually support.
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+#[cfg_attr(feature = "cache", derive(ruff_macros::CacheKey))]
 pub struct PythonVersion {
     pub major: u8,
     pub minor: u8,
@@ -43,9 +44,24 @@ impl PythonVersion {
         .into_iter()
     }
 
+    pub const fn latest() -> Self {
+        Self::PY313
+    }
+
+    pub const fn as_tuple(self) -> (u8, u8) {
+        (self.major, self.minor)
+    }
+
     pub fn free_threaded_build_available(self) -> bool {
         self >= PythonVersion::PY313
     }
+
+    /// Return `true` if the current version supports [PEP 701].
+    ///
+    /// [PEP 701]: https://peps.python.org/pep-0701/
+    pub fn supports_pep_701(self) -> bool {
+        self >= Self::PY312
+    }
 }
 
 impl Default for PythonVersion {