feat(python): add bypass_vector_index to sync api (#1947)

Hi lancedb team,

This PR adds the `bypass_vector_index` logic to the sync API, as
described in [Issue
#535](https://github.com/lancedb/lancedb/issues/535). (Closes #535).

Iv'e implemented it only for the regular vector search. If you think it
should also be supported for FTS, Hybrid, or Empty queries and for the
cloud solution, please let me know, and I’ll be happy to extend it.

Since there’s no `CONTRIBUTING.md` or contribution guidelines, I opted
for the simplest implementation to get this started.

Looking forward to your feedback!

Thanks!

---------

Co-authored-by: Will Jones <willjones127@gmail.com>

python/python/tests/test_db.py

@@ -681,3 +681,25 @@ def test_create_table_with_invalid_names(tmp_db: lancedb.DBConnection):
     with pytest.raises(ValueError):
         tmp_db.create_table("foo$$bar", data)
     tmp_db.create_table("foo.bar", data)
+
+
+def test_bypass_vector_index_sync(tmp_db: lancedb.DBConnection):
+    data = [{"vector": np.random.rand(32)} for _ in range(512)]
+    sample_key = data[100]["vector"]
+    table = tmp_db.create_table(
+        "test",
+        data,
+    )
+
+    table.create_index(
+        num_partitions=2,
+        num_sub_vectors=2,
+    )
+
+    plan_with_index = table.search(sample_key).explain_plan(verbose=True)
+    assert "ANN" in plan_with_index
+
+    plan_without_index = (
+        table.search(sample_key).bypass_vector_index().explain_plan(verbose=True)
+    )
+    assert "KNN" in plan_without_index