Move mediator commands into vscode-extension-web-ide

MR:

• feat: Add SecureMediatorCommandExecutor (!292 - merged)
• refactor: Move getHeaders out of AuthProvider (!298 - merged)

References

• Epic: Enable Web IDE Extension Marketplace for GitLab... (&11769 - closed)
• Use Web IDE AuthProvider instead of mediator co... (gitlab-vscode-extension#1253 - closed)
• Move non-auth mediator commands to ipc message ... (#317 - closed)
• Move mediator commands into vscode-extension-we... (#310 - closed)

Description

Once Use Web IDE AuthProvider instead of mediator co... (gitlab-vscode-extension#1253 - closed) is closed and the Web IDE uses the latest GitLab Workflow version, then we can safely remove the mediator commands.

To this iteratively, we'll try to simply replace the implementation of mediator/index.js with one that directly calls the methods defined in the vscode-mediator-commands package.

• Please note: The non-auth based mediator commands (like SET_HREF) cannot be moved to vscode-extension-web-ide and will need to be moved to IPC commands. This is covered by Move non-auth mediator commands to ipc message ... (#317 - closed)
• This all happens conditionally based on whether we have an authProvider or not.
• When the authProvider is present, the commands SHOULD NOT be registered globally in the vscode-bootstrap package.