Adding a version of AES-EAX using boringssl as underlying

library.

Things not done:
Things to check:
- The code does not use EVP. There are plans to just add code in assembly.
  Hence this is kind of backup code for the case where AES instructions are
  not available. Hence it is unclear whether using that horrible EVP interface
  makes sense.
- depot/google3/security/util/crypt/ contains a version of AES_EAX using
  EVP. The main problem with this implementation is that it is not thread safe.
- The code needs unaligned big-endian load and store. I have not been able
  to find a function that achieves this efficiently. Compilers can sometimes
  (but not always) optimize the load or stores.

PiperOrigin-RevId: 201177778
GitOrigin-RevId: 2601a0d6eb42804747718f283761774922cdf8f5