MINOR: jws: conversion to NIST curves name

MINOR: jws: conversion to NIST curves name

OpenSSL version greater than 3.0 does not use the same API when
manipulating EVP_PKEY structures, the EC_KEY API is deprecated and it's
not possible anymore to get an EC_GROUP and simply call
EC_GROUP_get_curve_name().

Instead, one must call EVP_PKEY_get_utf8_string_param with the
OSSL_PKEY_PARAM_GROUP_NAME parameter, but this would result in a SECG
curves name, instead of a NIST curves name in previous version.
(ex: secp384r1 vs P-384)

This patch adds 2 functions:

- the first one look for a curves name and converts it to an openssl
  NID.

- the second one converts a NID to a NIST curves name

The list only contains: P-256, P-384 and P-521 for now, it could be
extended in the fure with more curves.