CMake test framework plugin

[LecrisUT]

I want to sketch out some ideas for making tmt-cmake plugin:

• [ ] overall: how to write a tmt plugin? E.g. how can it be included in the .fmf files, how to overwrite it via an editable-like installation, how to minimize coupling with upstream
• [ ] overall: plugin will make sure CMake is available (maybe also ninja for good measure) from package manager
• [x] plan.prepare plugin: runs a configure-build (maybe also install) preset/traditional workflow
  • Source folder is in fmf tree, and build folder is in plan-data
  • Currently will limit that only one CMake prepare step is present
  • All other steps, must check that this step exists and use the build folder from this step (hence why only 1 CMake prepare step currently)
• [ ] test.framework plugin: run ctest for a build environment defined in previous feature
  • Currently considering, this just runs the full ctest suite with the filters defined in plan.discover
• [x] plan.discover plugin: convert test names and ctest labels to tmt tests and tags
  • https://cmake.org/cmake/help/latest/manual/ctest.1.html#show-as-json-object-model
  • Blocked by #2813
  • Currently considering, this step only generates one super-test and the user can use this step to add the ctest filters
• [ ] ~~plan.report plugin: recover junit results from ctest and forward it down~~
  • Need to rethink if this is necessary
• [ ] CMake: make tmt commands and/or python environment available in CMake
• [ ] CMake: add test wrapper to convert tmt-native test to ctest callable tests
• [ ] CMake: expose a tmt subcommand to be executed as part of ctest --build-and-test. E.g. thic could parse the build stdout/stderr, build folder artifacts, etc. as part of a regression test and pass it to something like beakerlib.