API joint for pulsar backend

[RobertIndie]

We need to make the frontend API caller be compatible with the pulsar backend.

Setup pulsar cluster: https://pulsar.apache.org/docs/en/standalone-docker/
API documentation for pulsar function: https://pulsar.apache.org/functions-rest-api/?version=2.7.2&apiversion=v3#tag/functions

The API includes:

• Get List of function
• Get function info
• Create function
• Update function
• Delete function
• Get function stats
• Get function status
• Start function
• Stop function