Create a rust_python_ast crate (#3370)

This PR productionizes @MichaReiser's suggestion in https://github.com/charliermarsh/ruff/issues/1820#issuecomment-1440204423, by creating a separate crate for the `ast` module (`rust_python_ast`). This will enable us to further split up the `ruff` crate, as we'll be able to create (e.g.) separate sub-linter crates that have access to these common AST utilities.

This was mostly a straightforward copy (with adjustments to module imports), as the few dependencies that _did_ require modifications were handled in #3366, #3367, and #3368.

crates/ruff_python_ast/src/logging.rs

@@ -0,0 +1,24 @@
+pub enum LoggingLevel {
+    Debug,
+    Critical,
+    Error,
+    Exception,
+    Info,
+    Warn,
+    Warning,
+}
+
+impl LoggingLevel {
+    pub fn from_attribute(level: &str) -> Option<Self> {
+        match level {
+            "debug" => Some(LoggingLevel::Debug),
+            "critical" => Some(LoggingLevel::Critical),
+            "error" => Some(LoggingLevel::Error),
+            "exception" => Some(LoggingLevel::Exception),
+            "info" => Some(LoggingLevel::Info),
+            "warn" => Some(LoggingLevel::Warn),
+            "warning" => Some(LoggingLevel::Warning),
+            _ => None,
+        }
+    }
+}