- ci/GHA: add cmake integration tests for Windows.
- ci/GHA: test `add_subdirectory` with Libgcrypt.
- make them run faster with prefill, unity, Ninja, omitting curl tool.
- add support for any build configuration.
- add old-cmake support with auto-detection.
- auto-detect Ninja.
- run consumer test apps to see if they work.
Also show the cryptography backend.
- add support for Windows.
- make it more verbose.
- re-add `ExternalProject` cmake consumer test. It's broken.
- tidy up terminology.
Cherry-picked from #1581Closes#1589