feat: dune build asks for relocking

[maiste]

This PR superseeds #10641. It displays an error to the user if the lock dir is out of sync with the dune-project when they try to execute dune build. It works with both the watch mode and the standard mode.

It requires #10852 to be merged first before merging this one. However, the code can be review before as they don't have direct dependencies.

It solves #10842.