In #2845 we ported the lancedb integration in lance-namespace to
lancedb. But that is too specific to RestNamespace. We can improve the
user entry point so that we can put local mode and future version of the
Flight SQL-based LanceDB server all behind this single
`LanceDbNamespaceClientBuilder` API.
Also I renamed `namespace` to `namesapceClient` to avoid confusion with
the namespace path.
After the refactoring on both client and server side, we should have the
ability to fully use lance REST namespace to call into LanceDB cloud and
enterprise. We can avoid having a JNI implementation (which today does
not really do anything except for vending a connection object), and just
use lance-core's RestNamespace.
We will at this moment have a LanceDbRestNamespaceBuilder to allow users
to more easily build the RestNamespace to talk to LanceDB Cloud or
Enterprise endpoint.
In the future, we could extend this further to also support the local
mode through DirectoryNamespace. That will be a separated PR.
