Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3230)

Commit aea145e3 removed some error codes that are generated
algorithmically: mapping alerts to error texts.  Found by
Andreas Karlsson.  This restores them, and adds two missing ones.
Reviewed-by: NMatt Caswell <matt@openssl.org>

Add script to find unused err/reason codes
Remove unused reason codes.
Remove entries for unused functions
Reviewed-by: NMatt Caswell <matt@openssl.org>