Seperate proxy and broker a single module

[Technoboy-]

Motivation

Usage:

messagingProtocols=mqtt-proxy
protocolHandlerDirectory=./protocols
mqttProxyListeners=mqtt-proxy://127.0.0.1:5682

Modifications

Describe the modifications you've done.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Documentation

Check the box below.

Need to update docs?

• doc-required

  (If you need help on updating docs, create a doc issue)

• no-need-doc

  (Please explain why)

• doc

  (If this PR contains doc changes)

[github-actions]

@Technoboy-:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)