Add Invariant Inputs as separate nodes

[jacobbieker]

Detailed Description

The paper uses land/sea mask, and orography masks with 0.1 degreex0.1 degree resolution for extra input. Currently, these inputs have to be added to the same nodes as the physical features, which also then means the outputs also include those variables, when they shouldn't need to. Adding them separately also means we can use the original resolution data if we want to, instead of downsampling to the same as the NWP grid.

Context

More data is better, and keeping data in native resolution is probably better.

Possible Implementation

Add another graph with the invariant features, and then a second input to the forward pass that can resuse the invariant features in multiple forward passes during rollout.