typo
minor refactoring, no functional changes
adding timing for multi-threaded case
Merge pull request #2013 from apavlenko:2.4_fd_sample
adding more than 4 channels random Mats support

if `Scalar:all` is used, Mats with 5+ channels cause errors
Merge pull request #2011 from ilya-lavrenov:dft_dct
Merge pull request #2015 from apavlenko:2.4_fix_ts_rng-fill