elliptic-curve: leverage `CtOption::into_option` #2765

Job	Run time
build (1.73.0, thumbv7em-none-eabi)	41s
minimal-versions	0s
build (1.73.0, wasm32-unknown-unknown)	33s
test (1.73.0)	26s
build (stable, thumbv7em-none-eabi)	28s
test (stable)	24s
test (nightly)	30s
build (stable, wasm32-unknown-unknown)	26s
	3m 28s

Provide feedback