[CI] new CI that covers uncommon build configurations

[mvieth]

An idea for a new CI (this was discussed a few times in comments of other issues or PRs): Build and test PCL with less-common build configurations, e.g.:

• C++17 or C++20 instead of C++14
• other values for CMAKE_BUILD_TYPE
• non-default versions of VTK, CMake, Eigen, etc.
• ...

Covering all possible combinations is probably not doable, maybe we could choose a few random combinations for each run. This CI could run maybe weekly or monthly. Running it for every PR does not seem feasible because of PCL's long build time. We could add a badge to the README to increase visibility of failures.