OpenSSL::paramnames: Use less magic perl

OpenSSL::paramnames: Use less magic perl

Constructions like $$cursor{whatever} and %$cursor{whatever} were ambiguous
in some perl versions, and it's still better to use the arrow syntax for the
way we use them, i.e. they can both be replaced with $cursor->{whatever}.

Fixes #21152
Fixes #21172

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21178)