[SparkConnect] Support url path in SparkConnect connection string

Current Spark Connect uses connection string like `sc://host1:15002`, which does not support a path in the url, e.g. not support value like `sc://host1/path1:15002`.

In Kubernetes, people can set up an Ingress to expose Spark Connect driver endpoint by a matching url, e.g. `http://host1/path1` can be routed to the driver endpoint. Need to update Spark Connect client to support this scenario.

This could be a Spark Client side change, e.g. in Python Spark Connect client, connect to server based on the host name, and intercept GPRC call to avoid path interfering GRPC protocol.

I am working on a prototype, also open to hear feedback / suggestions.

Start with the Spark Connect client and the prototype described in the issue, focusing first on connection-string parsing and how the client establishes gRPC calls. Confirm that a URL path can route through a Kubernetes Ingress without interfering with the gRPC protocol; done means Spark Connect connections using a path such as sc://host1/path1:15002 work successfully.

Written by the indexing model from the issue text.