Add option for Deterministic encoded protected and unprotected headers

[kentakayama]

Solves #573 .

This PR introduces deterministic_header option to COSE.new() constructor.
With this option, the headers will be deterministically encoded.

import cbor2
from cwt import COSE, COSEKey

sign_key = COSEKey.from_jwk({
    "kty": "EC",
    "alg": "ES256",
    "crv": "P-256",
    "x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
    "y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
    "d": "V8kgd2ZBRuh2dgyVINBUqpPDr7BOMGcF22CQMIUHtNM",
})

# UPDATED
ctx = COSE.new(alg_auto_inclusion=True, deterministic_header=True)
encoded = ctx.encode_and_sign(
    payload=b'a',
    key=sign_key,
    protected={"kid": "11"},
)
bstr_encoded_p = cbor2.loads(encoded).value[0]
encoded_p = cbor2.loads(bstr_encoded_p)
print(encoded_p)

displays {1: -7, 4: b'11'}, which is deterministically encoded.

[dajiaji]

Thanks for your contribution! It looks good to me.