Tests

Communicate `FieldPerp` consistently with other Fields #6010

Job	Run time
Fedora	12m 3s
Shared, OpenMP, 3D metrics	12m 9s
PETSc unreleased, ADIOS2, 3D metrics	14m 4s
Shared, release	9m 30s
Default options, Ubuntu 22.04	12m 41s
Debug, shared	12m 6s
Optimised, static	12m 2s
	1h 24m 35s

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