Integrate with "gkeep-files-sync" as pip3 executable package

[kanevk]

Background

The main part of the sync is offloaded into the package gkeep-files-sync.
The python library will be executed from the extension on a workspace start and will sync files into a specified "Notes root" directory.

Aim

Integrate with gkeep-files-sync as follows:

1. Add a UI message that asks the user to confirm the install of pip3 and gkeep-files-sync dependencies.
2. Start gkeep-files-sync on workspace open(if the server isn't already ON - check (3))
3. Mark the gkeep-files-sync as On via state file into shared storage for all extension instances.
4. Pass the config file path to the gkeep-files-sync service on execution