[code] fix gp cli while running next to jb product

[akosyakov]

Since #8025 gp open/preview always exepct JB product if it is enabled, so they break in VS Code Web. We should redesign it by relying on notification service on supervisor instead of env vars.

[andreafalzetti]

after a chat with @akosyakov we concluded that we could start working on this feature incrementally, by adding initially only the endpoint in supervisor and testing it internally by supervisor CLI.

Then, we could have a follow-up ticket to integrate with gp-cli and so on.

[andreafalzetti]

@mustard-mh and I started working on this, we pair programmed for a couple of hours today and made some progress. Besides adding two new endpoints to supervisor-api we have discussed the integration with gp cli.

We've considered 2 approaches, when users use gp open or gp preview:
A. gp cli calls supervisor which is now aware of the latest active IDE/client and supervisor executes the IDE's binary directly.
B. gp cli calls supervisor to retrieve the latest active IDE/client, and gp cli executes the IDE's binary.

The biggest downside of approach A is that we need to implement in supervisor 2 endpoints, one for open one for preview mapping all parameters and flags of those 2 commands. For example gp open has a --wait flag which we should make sure to pass to supervisor. We would stricly couple gp-cli commands and supevisor API.

Another small downside for approach A, is that potentially makes harder returning any error to the user. If the open and preview logic is executed from supervisor, we would need to pro-actively make sure we can report back to the user, in case of failure. Instead, if the logic lives in gp cli the error would be returned directly to the user.