jose-jwk: add support for p521 analogously to p256 and p384 #116

Job	Run time
no_std (1.65.0, thumbv7em-none-eabi)	3m 55s
no_std (1.65.0, wasm32-unknown-unknown)	3m 56s
test (1.65.0)	4m 8s
no_std (stable, thumbv7em-none-eabi)	19s
test (1.65.0, crypto)	4m 22s
no_std (stable, wasm32-unknown-unknown)	21s
test (1.65.0, p256)	4m 8s
test (1.65.0, p384)	4m 7s
test (1.65.0, rsa)	4m 13s
test (1.65.0, url)	4m 12s
test (1.65.0, p256,p384,rsa,url)	4m 22s
test (1.65.0, p256,p384)	4m 8s
test (1.65.0, p256,rsa)	4m 16s
test (1.65.0, p384,p256)	4m 9s
test (1.65.0, p384,rsa)	4m 20s
test (1.65.0, rsa,p256)	4m 12s
test (1.65.0, rsa,p384)	4m 18s
test (stable)	26s
test (stable, crypto)	34s
test (stable, p256)	25s
test (stable, p384)	27s
test (stable, rsa)	30s
test (stable, url)	24s
test (stable, p256,p384,rsa,url)	37s
test (stable, p256,p384)	28s
test (stable, p256,rsa)	33s
test (stable, p384,p256)	27s
test (stable, p384,rsa)	35s
test (stable, rsa,p256)	32s
test (stable, rsa,p384)	35s
minimal-versions / minimal-versions	47s
	1h 10m 46s

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