FixedList/Pair writeEntry is not opposite of primitiveEntry reading

Summary

Write a Pair or FixedList to a binary stream using 'writeEntry' and the result cannot be read as a dictionary.

Steps to reproduce

Run attached test app (bit of hack) and it fails with some stream error on the worker processor. Run on e.g. cavity decomposed into two.

Environment information

• OpenFOAM version : v2112

Possible fixes

Have specialised writeEntry for FixedList which does not use the << operator (or the write routine) to maintain backwards compatibility but instead outputs 'like a List'.Test-parallel-communicators.C