elliptic-curve: leverage `CtOption::into_option` (#1595) #2097

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 29s
build (1.65.0, wasm32-unknown-unknown)	1m 36s
minimal-versions	38s
build (stable, thumbv7em-none-eabi)	10s
build (stable, wasm32-unknown-unknown)	13s
test (1.65.0)	1m 40s
test (stable)	17s
	6m 3s

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