cmake: respect cflags/libdirs of native pkg-config detections

In Find modules with native pkg-config detection (libgsasl, libidn2,
libssh, libuv, nettle) use the C compiler flags returne

cmake: respect cflags/libdirs of native pkg-config detections

In Find modules with native pkg-config detection (libgsasl, libidn2,
libssh, libuv, nettle) use the C compiler flags returned by pkg-config.
Also use the library paths, and return the pathless library names.

Also:
- add these library paths to `libcurl.pc`/`curl-config`.
- fix libgsasl detection to use the detected header directory.

FindGSS already did this before this patch.

Fixes #14641

Closes #14652

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cmake: pkg-config 'found' message sync with native CMake

Cherry-picked from #14610

build: add `iphlpapi` lib for libssh on Windows

vcpkg doesn't need it because it fixes this with a libssh patch.
All other Windows builds need it.

(autotools build not tested.)

build: add `iphlpapi` lib for libssh on Windows

vcpkg doesn't need it because it fixes this with a libssh patch.
All other Windows builds need it.

(autotools build not tested.)

Closes #14618

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cmake: migrate dependency detections to Find modules

For: libgsasl, libidn2, libssh, libuv.

The new Find modules retain using `pkg-config` natively, not as a "hint"
for the CMak

cmake: migrate dependency detections to Find modules

For: libgsasl, libidn2, libssh, libuv.

The new Find modules retain using `pkg-config` natively, not as a "hint"
for the CMake-native detection. Of the pre-existing Find modules, only
FindNettle, and FindGSS (with customized code) work this way. Align
detection code for the new modules and add version detection for the
CMake-native paths.

Also, add CMake-native detection for `libgsasl`.

The remaining outlier in `CMakeLists.txt` is GnuTLS, which has
a CMake built-in Find module, but which lacks `pkg-config` support,
required for vcpkg. It remains unchanged.

Another part-outlier is `libssh`, which keeps requiring the trick
`find_package(libssh CONFIG QUIET)` for reasons I could not yet figure
out.

Closes #14555

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