Adding gRPC health check ping to be a part of is_live()

[Shah91n]

Summary

Currently, is_live() in the Python client only triggers REST calls and does not exercise the gRPC channel.

Proposed Solution

Having a gRPC health check ping as part of is_live() is beneficial in different scenarios where we need to check on channels.

Expected Behavior

client.is_live() triggers both REST and gRPC health checks.

Current Behavior

gRPC health check is only used during client initialization.