refactor: pull and use `bids_tools` docker image from the Gitlab CI container registry

[sebastientourbier]

This should involves the following tasks:

• Remove the bids_tools submodule
• Revise the Makefile: we should not build anymore the image but instead, we should log and pull the image directly from our container registry
• Update .env.template with new variables:
  • BIDS_TOOLS_VERSION: docker image version tag
  • BIDS_TOOLS_IMAGE: path to the docker image (e.g. registry.hbp.link/hip/bids-tools)