Allow custom path for `apollo.config` file

I currently work with a multi-folder monorepo with a dedicated folder for all the configs.
```
root
|_ configs
|_ apollo.config.js
|_ frontend-project-1
|_source files
|_ frontend-project-2
|_source files

```

I open separate workspaces in vscode for project-1 and project-2 instead of pointing to the repo's root.

From what I see in the docs, the extension will not work if `apollo.config.js` isn't present in the workspace repo (`frontend-project-1` or `frontend-project-2`), but I don't want to duplicate the config files in all the subfolders.
Is there any way I can provide a custom path for the config file for each subproject I import in my workspace?

┆Issue is synchronized with this [Jira Task](https://apollographql.atlassian.net/browse/NEBULA-1867) by [Unito](https://www.unito.io)
┆Link To Issue: https://apollographql.atlassian.net/browse/NEBULA-1867

Start by reviewing how the VS Code extension locates apollo.config.js relative to each workspace. Trace the configuration lookup for a project imported from a separate workspace, then define completion as allowing a custom config path per subproject without duplicating apollo.config.js files.

Written by the indexing model from the issue text.