Add Checker::import_from_typing (#17340)

Summary
--

This PR replaces uses of version-dependent imports from `typing` or
`typing_extensions` with a centralized `Checker::import_from_typing`
method.

The idea here is to make the fix for #9761 (whatever it ends up being)
applicable to all of the rules performing similar checks.

Test Plan
--

Existing tests for the affected rules.

crates/ruff_python_ast/src/python_version.rs

@@ -44,6 +44,11 @@ impl PythonVersion {
         .into_iter()
     }
 
+    /// The minimum supported Python version.
+    pub const fn lowest() -> Self {
+        Self::PY37
+    }
+
     pub const fn latest() -> Self {
         Self::PY313
     }