[Enhancement] Move all properties for the workflow classes to private

[jan-janssen]

The workflow should be used in four steps: (1) create workflow class and initialise parameters, (2) generate structures by calling generate_structures(), (3) evaluate structures with any external code, (4) analyse the computed results using analyse_structures(). Here is an example to calculate an energy volume curve from the documentation

from ase.build import bulk
from atomistics.calculators import evaluate_with_lammps, get_potential_by_name
from atomistics.workflows import EnergyVolumeCurveWorkflow

potential_dataframe = get_potential_by_name(
    potential_name='1999--Mishin-Y--Al--LAMMPS--ipr1'
)
workflow = EnergyVolumeCurveWorkflow(
    structure=bulk("Al", cubic=True), 
    num_points=11,
    fit_type="polynomial",
    fit_order=3,
    vol_range=0.05,
    axes=("x", "y", "z"),
    strains=None,
)
task_dict = workflow.generate_structures()
result_dict = evaluate_with_lammps(
    task_dict=task_dict,
    potential_dataframe=potential_dataframe,
)
fit_dict = workflow.analyse_structures(output_dict=result_dict)
print(fit_dict)

To encourage this behaviour the workflow should not have any public facing properties.