port remote connection client into lancedb (#194)

* to_df() is now async, added `to_df_blocking` to convenience
* add remote lancedb client to public lancedb
* make lancedb connection class understand url scheme
`lancedb+<connection_type>://<host>:<port>`.

python/tests/test_table.py

@@ -11,6 +11,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
+import functools
 from pathlib import Path
 
 import pandas as pd
@@ -23,6 +24,10 @@ class MockDB:
     def __init__(self, uri: Path):
         self.uri = uri
 
+    @functools.cached_property
+    def is_managed_remote(self) -> bool:
+        return False
+
 
 @pytest.fixture
 def db(tmp_path) -> MockDB: