fix (#1654): exporting to requirements.txt always prepends -e to dependencies (#1656)

* fix (locker): add `develop = false` in `poetry.lock` if set in `pyproject.toml`
fix (locker): read `develop` value from `poetry.lock` so it is respect when exporting to `requirements.txt`

* fix (test_installer): adopt expected result

* change (test_installer): move develop key from source to package in lock file

* fix (test_installer): make black happy