[WIP] Refactor the Makefile

[BboyKeen]

This PR brings in a new Makefile structure to offer a simpler development environment.
For the sake of simplicity and readibility, I purposefully used the Makefile as a task runner and removed almost all rules dependencies.

It introduces two Makefiles : one for the local environment and the other to build the production container.

Instead of relying on config files, we now rely on default env files. I introduced a possibility to override defaults by using a config/env.local which will be automatically read by the Makefile.

• The production Makefile still needs testing to make sure it bootstraps the production container properly.
• Same for Github Actions

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This PR depends on #1767 and on #1768