add incar_updates attribute to VASP workflows

[jacksund]

I'd like to improve the syntax for inheriting VASP settings and remove some boiler plate code in sub-flows. Rather than having devs use incar.copy() + incar.update(), we can replace those with a simple incar_updates attribute that is set instead. incar with then be a property method that builds the incar (and caches it for speedup).

current approach

class StaticEnergy__Vasp__WarrenLabHse(Relaxation__Vasp__WarrenLabHse):
    incar = Relaxation__Vasp__WarrenLabHse.incar.copy()
    incar.update(
        dict(
            IBRION=-1,
            NSW=0,
            LCHARG=True,
            LORBIT=11,
            LVHAR=True,
            LWAVE=True,
        )
    )

new approach

class StaticEnergy__Vasp__WarrenLabHse(Relaxation__Vasp__WarrenLabHse):
    incar_updates = dict(
        IBRION=-1,
        NSW=0,
        LCHARG=True,
        LORBIT=11,
        LVHAR=True,
        LWAVE=True,
    )

@SWeav02 let me know what you think of the proposed update. I'll wait on your approval before changing this throughout the repo

[SWeav02]

I like this a lot. When I was first building new workflows the current syntax was a little confusing.

[jacksund]

this is implemented now, but I'll update the guides for these changes in #592