Update test assets upon merge to main

[clmould]

Currently, there are 2 LT MFILEs that are tracked in PROCESS - one in the integration test data folder, and one in the unit test data folder. These files do not always get updated and variable renamings can be missed in these files.
These should be updated upon merge to main to reflect any code changes and be up to date.

One idea would be to not store MFILE assets but instead run a once through to create any MFILE assets that we need (as once through runs are quicker than running PROCESS entirely).