Conversion of the EC tests to use the framework.

Some refactoring done as well.

The prime_field_tests() function needs splitting and refactoring still.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3340)