Add `EcdsaCurve` trait impls #1925

Job	Run time
build (1.73.0, thumbv7em-none-eabi)	41s
build (1.73.0, wasm32-unknown-unknown)	42s
cross (armv7-unknown-linux-gnueabihf, 1.73.0)	1m 42s
doc	1m 8s
build (stable, thumbv7em-none-eabi)	33s
cross (armv7-unknown-linux-gnueabihf, stable)	1m 31s
build (stable, wasm32-unknown-unknown)	40s
cross (aarch64-unknown-linux-gnu, 1.73.0)	1m 28s
cross (aarch64-unknown-linux-gnu, stable)	1m 39s
test (i686-unknown-linux-gnu, 1.73.0, sudo apt update && sudo apt install gcc-multilib)	1m 48s
cross (powerpc-unknown-linux-gnu, 1.73.0)	1m 35s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	1m 46s
cross (powerpc-unknown-linux-gnu, stable)	1m 29s
test (x86_64-unknown-linux-gnu, 1.73.0)	1m 29s
test (x86_64-unknown-linux-gnu, stable)	1m 22s
	19m 33s

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