Revert `gitlab-vscode-ext-host` message port changes

MR:

Description

Based on the outcome of this issue, this approach of having a gitlab-vscode-ext-host message port proxy requests is not going to work. We need to revert these changes in the gitlab-web-ide project and the gitlab-web-ide-vscode-fork project.

Implementation plan

These are the changes we need to revert. It might be a clean revert, or there might be conflicts / something that's actually needed 🤷

Edited by Paul Slaughter