Remove proxy server

This MR aims to remove the octez-proxy-server. Indeed, this binary is not used and not maintained any more. In addition to that it is not feature complete and subsumed by the external RPC process.

On top of !14463 (merged)

Manually testing the MR

Check that there is no occurrence of the proxy-server any more.

Green CI

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR