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_formatter/src/lib.rs

@@ -15,7 +15,7 @@ use crate::comments::{
 pub use crate::context::PyFormatContext;
 pub use crate::options::{
     DocstringCode, DocstringCodeLineWidth, MagicTrailingComma, PreviewMode, PyFormatOptions,
-    PythonVersion, QuoteStyle,
+    QuoteStyle,
 };
 use crate::range::is_logical_line;
 pub use crate::shared_traits::{AsFormat, FormattedIter, FormattedIterExt, IntoFormat};