throw exception instead of returning false, if gcm tag validation evaluates to invalid.

[johanna-herrmann]

BREAKING CHANGE! Major update.

If aes gcm tag validation evaluates to invalid, an error / exception should be thrown, following the gcm specification: https://csrc.nist.rip/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-spec.pdf

Otherwise the user of this library has to check the validation which could be forgotten.

Libraries always should do all checks they can do, so library using developers can just use it.