refactor `cards::UniqueStandardCardsDeck<>` adding template constants

[schmouk]

Completed. Validated.

• playing_cards\unique_standard_cards_decks.h:
  • removed one redundant template parameter;
  • renamed and redefined some type wrappers;
  • modified accordingly the declarations of base template specializations;
  • enhanced the requirements specs on base template and methods implementations;
• playing_cards\standard_cards_decks.h:
  • added template constant parameter _DECKS_COUNT to the parameters of template specializations;
  • fixed type traits concepts;
• gTests:
  • enhanced the whole tests, for testing StandardCardsDecks as well as for testing UniqueStandardCardsDecks.