Improvements to passkey support:
- Changed how Private Key data is stored in the entries. This fixes issues e.g. on Discord Web and improves compatibility with KeepassXC
- Made CredentialID, PrivateKey and UserHandle fields protected
- changes BE/BS flags to 0/1 instead of false/true for compatibility with other tools
- removed the "passkey:" prefix in the URL field
- when searching for passkey, KP2A now correctly searches the KPEX_PASSKEY_RELYING_PARTY fields instead of URL
- fixes calculation of clientDataHash and origin-id extraction, fixing issues with non-browser based usage.