New ubuntu image contains cmakelang. So style check job now uses cmake-format from that.

Style check is upgraded to use clang-format-12. The relevant config file is updated to mention this version and all source files were reformatted with clang-format-12 (only a few files were modified).

Only jobs requiring cross-compiles use a separate (ubuntu multilib) image now, and none of the jobs use alpine3 image.