apps: test enc -P, -nosalt, -md and -iter options

apps: test enc -P, -nosalt, -md and -iter options

Several enc options were not exercised by any test. Add subtests
covering -P/-p printing of the derived salt, key and iv (deterministic
with a fixed salt and PBKDF2) together with the -nosalt variant that
omits the salt line, a -nosalt encrypt/decrypt round-trip, -md selecting
the key derivation digest with a mismatching digest that must fail to
decrypt, and -iter setting the PBKDF2 iteration count with a mismatching
count that must fail to decrypt.

Assisted-by: Claude:claude-opus-4-8
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Andrew Dinh <andrewd@openssl.org>
Reviewed-by: Daniel Kubec <kubec@openssl.foundation>
MergeDate: Mon Jul 27 09:11:47 2026
(Merged from https://github.com/openssl/openssl/pull/31948)