Add defaults api to openssl build

Add defaults api to openssl build

Build time defaults aren't great for windows, in which various macros
(like OPENSSLDIR) are selected at build time, but may be selected
differently at install time.  Add an internal defaults api to return the
build time constants on unix systems, but instead query registry keys
for the form:
HLKM\SOFTWARE\OpenSSL-{version}-{wininstallcontext}
Such that each built version of openssl may maintain its own set of
registry keys to identify these locations, and be set administratiely as
appropriate at install or run time

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24450)