feat(python): expose prefilter to lancedb (#522)

We have experimental support for prefiltering (without ANN) in pylance.
This means that we can now apply a filter BEFORE vector search is
performed. This can be done via the `.where(filter_string,
prefilter=True)` kwargs of the query.

Limitations:
- When connecting to LanceDB cloud, `prefilter=True` will raise
NotImplemented
- When an ANN index is present, `prefilter=True` will raise
NotImplemented
- This option is not available for full text search query
- This option is not available for empty search query (just
filter/project)

Additional changes in this PR:
- Bump pylance version to v0.8.0 which supports the experimental
prefiltering.

---------

Co-authored-by: Chang She <chang@lancedb.com>

python/tests/test_query.py

@@ -38,6 +38,7 @@ class MockTable:
         return ds.to_table(
             columns=query.columns,
             filter=query.filter,
+            prefilter=query.prefilter,
             nearest={
                 "column": query.vector_column,
                 "q": query.vector,
@@ -97,6 +98,25 @@ def test_query_builder_with_filter(table):
     assert all(df["vector"].values[0] == [3, 4])
 
 
+def test_query_builder_with_prefilter(table):
+    df = (
+        LanceVectorQueryBuilder(table, [0, 0], "vector")
+        .where("id = 2")
+        .limit(1)
+        .to_df()
+    )
+    assert len(df) == 0
+
+    df = (
+        LanceVectorQueryBuilder(table, [0, 0], "vector")
+        .where("id = 2", prefilter=True)
+        .limit(1)
+        .to_df()
+    )
+    assert df["id"].values[0] == 2
+    assert all(df["vector"].values[0] == [3, 4])
+
+
 def test_query_builder_with_metric(table):
     query = [4, 8]
     vector_column_name = "vector"