Update mentions of RNG parameters in the knowledge base

[gilles-peskine-arm]

Many knowledge base articles (rendered) show example programs that set up an RNG context and then call PK/X.509/TLS functions with f_rng, p_rng arguments. Starting with TF-PSA-Crypto 1.0 and Mbed TLS 4.0, all public API functions will no longer take explicit RNG arguments.

The goal of this issue is, for the KB articles that are concerned, to convey that different code is needed in Mbed TLS ≤ 3.x vs (TF-PSA-Crypto or Mbed TLS ≥4.0):

* Old: need to arrange an entropy object and a DRBG object. New: need to call `psa_crypto_init()` (this only needs to be shown in snippets that are meant to be a complete program or at least a major fragment, not in small snippets that are more focused).
* Old: pass RNG arguments to LMS/PK/X.509/TLS functions. New: no RNG arguments.

Articles that refer to low-level crypto APIs are out of scope here.