elliptic-curve: leverage `CtOption::into_option` (#1595) #1664

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 30s
build (1.65.0, wasm32-unknown-unknown)	2m 22s
build (stable, thumbv7em-none-eabi)	8s
build (stable, wasm32-unknown-unknown)	10s
test (1.65.0)	1m 40s
test (stable)	13s
minimal-versions / minimal-versions	27s
	6m 30s

Provide feedback