Improve environment variables

[peaklabs-dev]

1. Allow setting up a production environment variable file path (in the git repo where is the .env file) and a staging file path (2 different files and paths if needed) - the variables from the Git repo will be automatically loaded into the environment variable tab and the compose file.
2. If you define environment variables in the env tab, they should be parsed and added to the compose file automatically (Otherwise, if you use envs that are only in the env tab, but not manually added to the compose file, they will not appear in the container, which is confusing.) -> currently only variables defined in the compose file are automatically parsed into the env tab, it should also be the other way around (like 2 way sync) - parse the env tab variabels into the compose file somehow.
3. Ability to use shared variables directly like this: TEST={{team.SENDGRID_API_KEY}} in compose files without having to do the following manual setup: [Bug]: Shared variables not substituted in Docker Compose projects #2169 (comment)
   Example compose file with a shared variable (this should be possible - maybe needs another syntax but should work):

services:
  mariadb:
    image: mariadb
    environment:
      - MYSQL_USER_PASSWORD={{team.MYSQL_PASSWORD}}