EVP_CIPHER Documentation updates

EVP_CIPHER Documentation updates

EVP_EncryptInit.pod now follows the pattern used in EVP_DigestInit.pod.
i.e.
'=item' is used for methods
PARAMETERS and CONTROLS sections have been added.

The PARAMETERS list has been moved from provider-cipher.pod (this file just
has a link now).
Missing fields were updated.

The CONTROLS shows the mappings to OSSL_PARAM keys.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15416)