ecdsa: remove `SignPrimitive`/`VerifyPrimitive` traits #2010

Job	Run time
build (1.73.0, thumbv7em-none-eabi)	42s
cross (armv7-unknown-linux-gnueabihf, 1.73.0)	1m 36s
build (1.73.0, wasm32-unknown-unknown)	2m 9s
cross (armv7-unknown-linux-gnueabihf, stable)	1m 33s
build (stable, thumbv7em-none-eabi)	42s
cross (aarch64-unknown-linux-gnu, 1.73.0)	1m 24s
build (stable, wasm32-unknown-unknown)	41s
cross (aarch64-unknown-linux-gnu, stable)	1m 27s
cross (powerpc-unknown-linux-gnu, 1.73.0)	1m 38s
test (i686-unknown-linux-gnu, 1.73.0, sudo apt update && sudo apt install gcc-multilib)	1m 55s
doc	56s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	1m 54s
cross (powerpc-unknown-linux-gnu, stable)	1m 30s
test (x86_64-unknown-linux-gnu, 1.73.0)	1m 37s
test (x86_64-unknown-linux-gnu, stable)	1m 28s
	21m 12s

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