Discontinue legacy resource support after 2024 (or sooner)

[stephen-soltesz]

A condition of accepting change for #184 is that we include an absolute end date for support.

If these features still remain after 2024, they should be unconditionally purged.

[bassosimone]

Pull request #252 implements a more minimal approach that is enough to support migration off using locate by known integrators that are still working on this. No known integrator is using ndt5 anymore and all they need is a minimal shim to avoid breaking documentational only code calling mlab-ns.

[bassosimone]

We have now merged #252. Obviously, more work is required before calling this issue complete. Regardless, I just wanted to chip and celebrate doing some progress towards decommissioning! 🥳