ENGINE modules aren't special, so call them MODULES

ENGINE modules aren't special, so call them MODULES

The only thing that makes an ENGINE module special is its entry
points.  Other than that, it's a normal dynamically loadable module,
nothing special about it.  This change has us stop pretending anything
else.

We retain using ENGINE as a term for installation, because it's
related to a specific installation directory, and we therefore also
mark ENGINE modules specifically as such with an attribute in the
build.info files.

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/8147)