There is no need to have `RSAPrivateKey`, `RSAPublicKey`, `ECPrivateKey`
and `ECPublicKey` to be templatize to utilize different implementation
of numbers.
In order for public/private key serialization to work correctly we must
store the size of the key because P-521 cannot be stored as full words
inside `UnsignedBigInteger` and therefore is exported as the wrong
length (68 instead of 66).
This makes it also possible to refactor some methods and cleanup
constants scattered around.
Gets almost all import/export tests, expect the JWK ones that calculate
the public key on export. The `SECPxxxr1` implementation currently fails
to do calculations for P-521.
Added basic EC private and public key definitions as well as ASN.1
encoding and decoding.
A lot of refactoring can be made around the ASN.1 processing (here and
in other parts of the codebase) by utilizing what is available
in `LibCrypto::Certificate` as macros, but I think it's outside the
scope of implementing ECDH support for WebCryptoAPI.
