PwBandStructureWorkChain: Deprecate and fix

[mbercx]

Fixes #687

The PwBandStructureWorkChain is a legacy version of a band structure work
chain with a pre-defined protocol, mostly used for previous tutorials.
However, now that the PwBandsWorkChain has been equipped with a protocol
through the get_builder_from_protocol() method, it no longer serves a
purpose and should be deprecated.

However, there were still two issues with running the work chain that
needed to be fixed, since users were still running it and it is still
supported until v4.0.0:

• The get_pseudos_from_dict() method, used by the work chain, only
  accepted UpfData from the aiida-pseudo package. Since the work chain
  was often run with legacy UpfData, this raised errors for several
  users. This is fixed by also accepting the legacy UpfData here.
• There was a small bug in the PwRelaxWorkChain when using the
  relaxation_scheme input (which is also deprecated). Basically, at some
  point in the work chain, the base input port was checked for the
  pw.parameters.CONTROL.calculation value, but in case the user doesn't
  specify this input (which passes validation when the relaxation_scheme
  is provided), this would raise a KeyError when running the work chain.
  This is fixed by obtaining the calculation value from the context
  instead.

[mbercx]

@sphuber do I still have to add tests for this, since the inputs related to the bugs have been deprecated anyways? 😬

[sphuber]

@sphuber do I still have to add tests for this, since the inputs related to the bugs have been deprecated anyways? grimacing

If you have tested it locally and verified that it works, it is fine to omit the unit tests for this legacy workchain

[mbercx]

If you have tested it locally and verified that it works, it is fine to omit the unit tests for this legacy workchain

I followed the tutorial instructions and: 🙃

$ verdi process status 527
PwBandStructureWorkChain<527> Finished [0] [3:results]
    └── PwBandsWorkChain<541> Finished [0] [7:results]
        ├── PwRelaxWorkChain<543> Finished [0] [3:results]
        │   ├── PwBaseWorkChain<546> Finished [0] [6:results]
        │   │   ├── create_kpoints_from_distance<548> Finished [0]
        │   │   └── PwCalculation<552> Finished [0]
        │   └── PwBaseWorkChain<561> Finished [0] [6:results]
        │       ├── create_kpoints_from_distance<563> Finished [0]
        │       └── PwCalculation<567> Finished [0]
        ├── seekpath_structure_analysis<574> Finished [0]
        ├── PwBaseWorkChain<581> Finished [0] [6:results]
        │   ├── create_kpoints_from_distance<583> Finished [0]
        │   └── PwCalculation<587> Finished [0]
        └── PwBaseWorkChain<595> Finished [0] [6:results]
            └── PwCalculation<598> Finished [0]

[sphuber]

I followed the tutorial instructions and: upside_down_face

That's all one can ask for 👍