Inplace volumes: check that all facies are checked

[mferrera]

Standardization: Allows for computing facies fractions, ensuring it's not just a subset of them but all of them

Then you can provide the users with facies fraction and ensure that everything is included in the volumes that are exported.

[tnatt]

Seems not as trivial task as first expected - turns out it is only possible to see which facies is selected but not how many facies exists in total. Then the only way to find the existing facies is to load the grid parameter values and get the codenames for the unique facies codes present.
I think this task is best set on hold until we start adressing the .fmu folder https://github.com/equinor/atlas/issues/53; what facies is existing in the model is suitable as part of the FMU model masterdata.