Remove obsolete documentation about cryptographic mechanisms

[gilles-peskine-arm]

There is some documentation about supported cryptographic mechanisms in doxygen/input/doc_*.h in Mbed TLS, visible in the Doxygen-rendered documentation for e.g. hashes.

In 3.6, this documentation is out of date (e.g. missing SHA3), and only mentions legacy APIs, not PSA APIs.

In 4.0, this documentation is additionally in the wrong project.

Goal of this task: update or remove this documentation in 3.6, remove it in 4.0.

Out of scope: replacement documentation for TF-PSA-Crypto. That is covered by Mbed-TLS/TF-PSA-Crypto#561.

[Shulcare]

Not sure if this is the right place, but I noticed there is an outdated documentation for alternative implementations, too. It is based on the _ALT macros which were completely removed in v4.0.