Few functions & classes of conan.tools not documented

[SpaceIm]

Several functions & classes exposed in conan.tools are not documented:

conan.tools.build.valid_min_cppstd (available since conan 1.50.0) conan.tools.cmake.CMakeFileAPI (available since conan 1.39.0) conan.tools.files.collect_libs (available since conan 1.46.0) conan.tools.files.CppPackage (available since conan 1.39.0) conan.tools.microsoft.vs_layout (available since conan 1.45.0)