Simplify cloud credential mounting in local runner

[RobbeSneyders]

Currently the user needs to manually provide the location of the cloud credentials to mount with the local runner, which is quite complex. Eg:

fondant compile pipeline:pipeline --extra-volumes "$HOME/.config/gcloud/application_default_credentials.json:/root/.config/gcloud/application_default_credentials.json:ro"

These cloud credentials have a default location on the user system, so we could make it easier. We can either:

• Automatically add them without the user having to specify anything. This is the simplest approach for the user, but would also mount the credentials when not needed, and could expose them to third party components.
• Add a flag to add them, and use the default path. Eg.

  fondant compile pipeline:pipeline --auth-gcp
  

The user can still use the --extra-volumes argument to pass a non-default location.

[RobbeSneyders]

Closed in #548