Validate Wallet Instance Attestation signature algorithm

[dzarras]

When ClientAthentication.AttestationBased is used with a Wallet Instance Attestation, we must verify that the WIA is signed with one of the following JWS Algorithms:

1. ES256, i.e. ECDSA with SHA-256 on P-256 Curve
2. ES384, i.e. ECDSA with SHA-384 on P-384 Curve
3. ES512, i.e. ECDSA with SHA-512 on P-512 Curve

[dzarras]

Relates to #482