Make EVP_PKEY_CTX initialization more precise

There is a vagueness around how the provider data (algorithm name and
property query string) is initialized in the presence of an engine.
This change modifies this slightly so that the algorithm name for use
with providers is never set if the initilization was given an engine.

This makes it easier for other functions to simply check ctx->algorithm
to see if the context is meant to be used for strictly legacy stuff or
not.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10308)