CRL: Refactoring and tests for extensions, entries, and serial number duplicates

CRL: Refactoring and tests for extensions, entries, and serial number duplicates

Refactoring and added tests for extensions, entries, and serial number
duplicates. The tests intentionally reflect the current behavior and existing
error states, which are not always clearly distinguished (e.g., duplicate
extensions vs. parsing errors). This serves as a baseline; follow-up work may
improve error handling or explicitly mark some cases as wontfix.

Signed-off-by: Daniel Kubec <kubec@openssl.foundation>
Reviewed-by: Tomas Mraz <tomas@openssl.foundation>
Reviewed-by: Matt Caswell <matt@openssl.foundation>
MergeDate: Wed May 13 07:36:49 2026
(Merged from https://github.com/openssl/openssl/pull/30349)