Passkeys: Add publicKey to register response

[varjolintu]

Adds a DER SubjectPublicKeyInfo to the passkey registration response. We are currently not writing this, even if It is part of the specification https://w3c.github.io/webauthn/#sctn-public-key-easy:

User agents MUST be able to return a non-null value for getPublicKey() when the credential public key has a COSEAlgorithmIdentifier value of:
-7 (ES256), where kty is 2 (with uncompressed points) and crv is 1 (P-256).
-257 (RS256).
-8 (EdDSA), where crv is 6 (Ed25519).

Fixes a passkey creation on Logitech site https://id.logi.com.

Testing strategy

Manually with: keepassxreboot/keepassxc-browser#2782
Tested https://webauthn.io with all three different algorithms to verify the response has the new publicKey in base64 format in the browser logs.

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[varjolintu]

Need to add some exceptions for Botan 2.

[droidmonkey]

Can we add a test for this response?

[varjolintu]

Can we add a test for this response?

I'll try. We use predefined values for the keys so it should be possible.

EDIT: We are not actually creating any keys in the tests so.. I'll try to modify the tests so we can create actual keys with const predefined data.

[varjolintu]

Modified the testRegister() unit test. It is using a new variable for const data when creating an actual ECDSA private key. Cleaned up the variable names a bit. All didn't match with the ones specified in header files.

And of course the private key data changes affected to some other tests too.