Implementation of XAES-256-GCM with EVP_AEAD

[ttungle96]

Issues:

1. Add XAES-256-GCM, which is extended AES-256-GCM with a derived key mode proposed by Filippo Valsorda in 2023, followed by a specification released in 2024.
2. This implementation supports EVP_AEAD API, allows configuration to use either FIPS-compliant CMAC available in AWS-LC, or an optimized CMAC dedicated to the specific use case of XAES-256-GCM from XAES-256-GCM #2652.
3. Support varying nonce sizes: 20 ≤ b ≤ 24 based on the extension: https://eprint.iacr.org/2025/758.pdf#page=24

Description of Changes

Implementation for API EVP_AEAD of XAES-256-GCM is appended to e_aes.c, and the tests are appended to aead_test.cc.

Testing

We use the test vectors provided here:
https://github.com/C2SP/C2SP/blob/main/XAES-256-GCM.md
https://github.com/C2SP/C2SP/blob/main/XAES-256-GCM/openssl/openssl.c
https://github.com/C2SP/C2SP/blob/main/XAES-256-GCM/go/XAES-256-GCM_test.go

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.