elliptic-curve: add missing `Debug` impls #2883

Job	Run time
build (1.73.0, thumbv7em-none-eabi)	43s
build (1.73.0, wasm32-unknown-unknown)	38s
minimal-versions	0s
build (stable, thumbv7em-none-eabi)	34s
test (1.73.0)	33s
build (stable, wasm32-unknown-unknown)	31s
test (stable)	27s
test (nightly)	27s
	3m 53s

Provide feedback