Fix [Incorrect SHAKE APIs]

[rdubois-crypto]

/*## Description

As a XOF, SHAKE is intended to be used dynamically (squeeze function being called at will, without prior knowledge at init of the output length).

Your environment

Not relevant

Steps to reproduce

APIs of final doesn't include a length. Prior knowledge at init is required.

Expected behaviour

A cx_shake128_squeeze(state, buff, outlen) shall be available instead of final.

Actual behaviour

It is expected to know desired output length at init. A XOF enables dynamic generation.

Logs

Not relevant

Proposed solution

Implemeent cx_shake128_squeeze(state, buff, outlen) and cx_shake256_squeeze(state, buff, outlen)
*/

[rdubois-crypto]

Note also that while there are "init functions" in the lcx_sha3.h files, no "final" functions is provided.

A possible fix without changing the APIs would be that an internal flag detects if final has already been called or not. If yes, the padding step (finalize), shall not be done.

It would the be possible to make the dynamic calls to squeeze by iterating on "final"