Warn when trying to `uv sync` a package without build configuration (#7420)
This enhances `uv sync` logic in order to detect and warn if it is
trying to operate on a packaged project with entrypoints.
Ref: https://github.com/astral-sh/uv/issues/6998#issuecomment-2329291764
Closes: https://github.com/astral-sh/uv/issues/7034