Refactoring of CField struct to include gridindexingtype and interp_method #29

Job	Run time
py3.12 \| macos \| unit tests	9m 49s
py3.12 \| macos \| integration tests	14m 22s
py3.12 \| ubuntu \| unit tests	15m 0s
py3.12 \| ubuntu \| integration tests	18m 11s
py3.12 \| windows \| unit tests	23m 57s
py3.12 \| windows \| integration tests	31m 34s
py3.10 \| ubuntu \| unit tests	14m 10s
py3.11 \| ubuntu \| unit tests	14m 5s
	2h 21m 8s

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