- The internal storage location of finite-area changes from being
piggybacked on the polyMesh registry to a having its own dedicated
registry:
* allows a clearer separation of field types without name clashes.
* prerequisite for supporting multiple finite-area regions (future)
Old Locations:
```
0/Us
constant/faMesh
system/faMeshDefinition
system/faSchemes
system/faSolution
```
New Locations:
```
0/finite-area/Us
constant/finite-area/faMesh
system/finite-area/faMeshDefinition (or system/faMeshDefinition)
system/finite-area/faSchemes
system/finite-area/faSolution
```
NOTES:
The new locations represent a hard change (breaking change) that
is normally to be avoided, but seamless compatibility handling
within the code was found to be unworkable.
The `foamUpgradeFiniteArea` script provides assistance with migration.
As a convenience, the system/faMeshDefinition location continues
to be supported (may be deprecated in the future).
b5435cc83e