Removing Field.to_write and FieldSet.to_write methods #752

Job	Run time
py3.13 \| macos \| integration tests	22m 34s
py3.13 \| ubuntu \| integration tests	13m 36s
py3.13 \| macos \| unit tests	7m 23s
mypy	3m 29s
py3.13 \| windows \| integration tests	23m 24s
py3.13 \| ubuntu \| unit tests	9m 34s
py3.10 \| ubuntu \| integration tests	13m 47s
py3.13 \| windows \| unit tests	13m 57s
py3.10 \| ubuntu \| unit tests	10m 36s
py3.11 \| ubuntu \| unit tests	10m 9s
py3.12 \| ubuntu \| unit tests	10m 21s
merge-test-artifacts	2s
	2h 18m 52s

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