Add IVFSQTurboQSearchParameters to __init__.pyi stub (#5304)

Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/5304

Add IVFSQTurboQSearchParameters to the authoritative __init__.pyi type stub.

TurboQuant was added to ScalarQuantizer in D102408184, which introduced
IVFSQTurboQSearchParameters in IndexScalarQuantizer.h. The struct controls
two new per-search parameters:
- qb: query quantization bits for MSE pre-screening (0 = float path,
  1-8 = integer popcount path)
- int_qjl: use integer popcount for the QJL sign-bit stage (requires qb > 0)

IndexScalarQuantizer.h is `%include`d in swigfaiss.swig so SWIG wraps the
struct at runtime. However, __init__.pyi (the authoritative Pyre type source
since D107274305) was not updated when the struct was added. Any Pyre-checked
code that uses IVFSQTurboQSearchParameters receives [missing-attribute] errors.

Pattern matches the approach used in D107508282, which added
SearchParametersHNSW and SearchParametersPQ for the same gap.

Reviewed By: limqiying, mnorris11

Differential Revision: D108001955

fbshipit-source-id: 6cfbb0dddea1e09562b8185888c571aea229b747

faiss/python/__init__.pyi

@@ -2290,6 +2290,12 @@ class IVFSearchParameters(SearchParameters):
     sel: IDSelector | None
     def __init__(self) -> None: ...
 
+class IVFSQTurboQSearchParameters(IVFSearchParameters):
+    qb: int
+    int_qjl: bool
+
+    def __init__(self) -> None: ...
+
 # IVF Statistics tracking
 class IndexIVFStats:
     nq: int  # number of queries run

tests/test_swig_wrapper.py

@@ -146,6 +146,14 @@ class TestSWIGWrap(unittest.TestCase):
         with self.assertRaises(AttributeError):
             index.centered2 = False
 
+    def test_ivfsq_turboq_search_parameters(self):
+        params = faiss.IVFSQTurboQSearchParameters()
+        self.assertEqual(params.qb, 0)
+        self.assertFalse(params.int_qjl)
+        params.qb = 4
+        params.int_qjl = True
+        self.assertEqual(params.qb, 4)
+        self.assertTrue(params.int_qjl)
 
 
 class TestRevSwigPtr(unittest.TestCase):