32-bit platforms fail to allocate the 2 GiB of RAM that argon2 requires in the RFC9580 test vector.
Thus, this PR skips the test for 32-bit platforms and adds a separate test vector with smaller parameters.

Argon2 s2k parameters were previously not validated on the OpenPGP side before invoking Argon2, which could lead to potential panics during runtime. This commit introduces a validation step for these parameters before calling Argon2, ensuring that invalid inputs are caught early and an appropriate error is returned instead of risking a panic.

Co-authored-by: Daniel Huigens <[email protected]>

Allow explicitly indicating whether AEAD is supported when creating
an SKESK packet, instead of looking at config.AEAD().

The config is no longer reliable, and we shouldn't mix SKESKv3 and
SEIPDv2, for example.

…ricKeyEncryptedReuseKey

These functions don't allow explicitly indicating whether AEAD is
supported and are thus prone to misuse. The *AEAD versions should
be used instead.

Document that the `aeadSupported` parameter passed to
`SerializeEncryptedKeyAEAD[withHiddenOption]`,
`SerializeSymmetricKeyEncryptedAEADReuseKey`, and
`SerializeSymmetricallyEncrypted` must match.

Advertise SEIPDv2 and AEAD modes during key generation only if AEAD configuration is enabled.

Improve AEAD handling

* feat: Improve error message for decryption with a session key

* chore: Add explicit error message strings to tests

* feat: Update SEIPD test vectors

* chore: Move expected error to the old position

* feat: Unify mdc integrity error

* feat: Add aead test for missing last auth tag

* docs: Add comments when handling parsing errors

* feat: Unify parsing errors in SEIPDv1 decryption

Adds a flag InsecureAllowDecryptionWithSigningKeys that allows to use keys for decryption 
that are marked as signing keys only.