Tests

Communicate `FieldPerp` consistently with other Fields #6030

Job	Run time
Fedora	19m 19s
Shared, OpenMP, 3D metrics	13m 44s
Debug, shared	28m 50s
Shared, release	17m 34s
PETSc unreleased, ADIOS2, 3D metrics	23m 14s
Optimised, static	16m 53s
Default options, Ubuntu 22.04	13m 40s
	2h 13m 14s

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