* enable reference implementation for CTCGreedyDecoder single layer tests
* update unit test to have blnak_index
* remove merge_repeated disable flag for CPU test because CPU impl always
merge
* add CTCGreedyDecoder single layer tests for CPU
* changes to match xPU implementations
* apply reviewers suggestions
Co-authored-by: Patryk Elszkowski <patryk.elszkowki@intel.com>