Fix crash with constraints

When using equality constraints for optimisation, pybind11 was trying to copy by-reference arguments without a copy constructor. By adding a dummy cast with a reference return value policy, this copy is avoided. This should hopefully fix a crash observed when using a StdVector for equality constraint multipliers.

Fix dylib location on macOS

This fixes a couple of issues on macOS: dylibs not being found because of how the loader works, and the CMake build system finding the wrong Python version when building ROL, thus being incompatible with a given wheel.

Build on Apple silicon

This uses the new macos-14 ARM-based runner, which should allow us to make binary packages for all supported platforms. With the introduction of setuptools_scm to automatically manage versions from tags, this also drops support for Python 3.7.

Fix packaging

Explicitly name Actions artifacts

For some reason this wasn't an issue before, perhaps the bump to the
artifact actions has broken this.

Automatic packaging release

This is the first release since moving the checkpointing-focused branch of ROL to master. It's also a test of the automatic packaging for PyPI, both on manylinux and macOS.