Match CPython quotechar escaping when doublequote is disabled (#8953)

Let quote-only fields use the existing unquoted escaping path and enable
the existing CPython regression test.

Tested: test_csv, CSV snippet, 240 CPython comparisons, workspace and C-API tests, Clippy, prek
Assisted-by: Codex:gpt-6.1-sol

Lib/test/test_csv.py

@@ -228,7 +228,6 @@ class Test_Csv(unittest.TestCase):
         self._write_test(['a','',None,1], '"a","",,"1"',
                          quoting = csv.QUOTE_NOTNULL)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_write_escape(self):
         self._write_test(['a',1,'p,q'], 'a,1,"p,q"',
                          escapechar='\\')

crates/stdlib/src/csv.rs

@@ -1246,7 +1246,7 @@ mod _csv {
     fn field_needs_quotes(data: &[u8], dialect: &PyDialect) -> bool {
         data.iter().any(|&byte| {
             byte == dialect.delimiter
-                || dialect.quotechar == Some(byte)
+                || (dialect.doublequote && dialect.quotechar == Some(byte))
                 || matches!(byte, b'\r' | b'\n')
         }) || data_contains_lineterminator_char(data, dialect)
     }