Compute deconvolution parameters in FlashCamExtractor only as needed #4452

Job	Run time
docs	8m 9s
lint	13s
tests (ubuntu-latest, 3.10, mamba)	11m 59s
tests (ubuntu-latest, 3.10, pip)	12m 51s
tests (ubuntu-latest, 3.11, mamba)	12m 7s
tests (ubuntu-latest, 3.12, mamba, codecov)	13m 5s
tests (ubuntu-latest, 3.12, pip)	15m 50s
tests (macos-13, 3.10, pip)	12m 14s
tests (macos-14, 3.12, mamba)	9m 34s
	1h 36m 2s

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