Keep poetry.lock modification time newer than pyproject.toml, after relevant commands

• I have searched the issues of this repo and believe that this is not a duplicate.
• I have searched the FAQ and general documentation and believe that my question is not already covered.

Feature Request

After doing operations like add/remove/update that both updates pyproject.toml and refreshes poetry.lock, please complete the operation leaving poetry.lock's modification time to be newer than pyproject.toml's.

Not only is this conceptually proper to match the direction of dependency, it means Makefiles can be used to implement "auto-poetry install if needed" behavior, e.g.:

• https://github.com/python-poetry/poetry/issues/75#issuecomment-399514444
• https://medium.com/aigent/makefiles-for-python-and-beyond-5cf28349bf05

The comment in #75 suggests this already used to be the case at some point. I'm currently using 1.2.2.

Start by tracing the add, remove, and update commands mentioned in the issue, focusing on how each writes pyproject.toml and poetry.lock. Done means those operations leave poetry.lock with a newer modification time than pyproject.toml, while preserving the existing lock refresh behavior.