openssl: Don't ignore CA paths when using Windows CA store (redux)

openssl: Don't ignore CA paths when using Windows CA store (redux)

.. and remove 'experimental' designation from CURLSSLOPT_NATIVE_CA.

This commit restores the behavior of CURLSSLOPT_NATIVE_CA so that it
does not override CURLOPT_CAINFO / CURLOPT_CAPATH, or the hardcoded
default locations. Instead the native Windows CA store can be used at
the same time.

---

This behavior was originally added over two years ago in abbc5d60
(#5585) but then 83393b1a (#7892) broke it over a year ago, I assume
inadvertently.

The CURLSSLOPT_NATIVE_CA feature was marked experimental and likely
rarely used.

Ref: https://github.com/curl/curl/pull/5585
Ref: https://github.com/curl/curl/pull/7892
Ref: https://curl.se/mail/lib-2023-01/0019.html

Closes https://github.com/curl/curl/pull/10244