code-server spawned within code-server inherits plugin paths of parent code-server when it should not

[jsjoeio]

@bryphe-coder and I found a bug in code-server running in Coder and realized it takes you to the plugins/applications page instead of showing you the editor.

We have logic here to remove these but since Coder uses CS_PLUGIN, it doesn't get removed in the user's environment.

Todos

• rename CS_PLUGIN to CODE_SERVER_PLUGIN
• support both for backwards compatbility