EVP: Adapt EVP_PKEY_{set1,get1}_encoded_public_key()

EVP: Adapt EVP_PKEY_{set1,get1}_encoded_public_key()

These functions are modified to use EVP_PKEY_set_octet_string_param()
and EVP_PKEY_get_octet_string_param() instead of evp_keymgmt_set_params()
and evp_keymgmt_get_params().
To accomplish this fully, EVP_PKEY_get_octet_string_param() is changed
slightly to populate |*out_sz| with the return size, even if getting
the params resulted in an error.

We also modify EVP_PKEY_get_utf8_string_param() to match
EVP_PKEY_get_octet_string_param()

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14056)