COREPACK_ENABLE_AUTO_PIN should be possible to set on a project level

[SimonMorkSaetre]

I encountered an issue where the packageManager field was added every single time I installed with yarn. We don't allow the field to be added to our package.json (I have tried but it's a management problem), so the field has to be removed manually every time one reinstalls packages. Yes one can add an environment variable on an OS level, but it has to be done on every single device that is being used with our codebase. It adds a lot of extra work for us.

Please either disable the packageManager field by default or add a way to disable it on a project level.

[MikeMcC399]

• related to COREPACK_ENABLE_AUTO_PIN should default to 0 #485