Change gRPC implementation to layer on top of HTTP2 transport

[daneshk]

Description:
This issue is to track changes we need to do to layer gRPC support on top of our HTTP2 transport and get rid of gRPC netty dependencies.

Current Ballerina gRPC implementation depends on grpc-netty implementation to setup http2 connection. we need to use transport-http dependency instead of that.

Steps to reproduce:
N/A, this is an improvement.

Affected Versions:
N/A, this is an improvement.

OS, DB, other environment details and versions:
N/A, this is an improvement.

Related Issues (optional):
None

Suggested Labels (optional):
improvement

Suggested Assignees (optional):
@daneshk