Final cleanup after move to leaner EVP_PKEY methods

Final cleanup after move to leaner EVP_PKEY methods

Now that KEYMGMT method pointers have moved away from the diverse
methods that are used with EVP_PKEY_CTX, we no longer need to pass
special argument to evp_generic_fetch() and evp_generic_do_all().

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10309)