Declare cipher_auth_{en,de}crypt_ext()
Declare cipher_auth_{en,de}crypt_ext()

Work in progress: next steps are to implement and test it.

Compared to the existing non-ext version:

- to separate tag parameter
- explicit output_len parameter

Also, this version will retain support for NIST_KW (hence documents it), while
the non-ext version will lose it in a few commits.

Signed-off-by: Manuel Pégourié-Gonnard <4ba0d615aeeda88e422ca8fba28fe2938485facf@arm.com>

Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls