Add consecutive_string_generator utility function and refactor player name generation

[hmasdev]

This pull request adds a new utility function called consecutive_string_generator that generates strings with a prefix and a number. It is used to refactor the player name generation in the DefaultGameMaster class. The function takes a prefix, start number, and step as arguments and returns a generator that yields consecutive strings with the specified prefix and number. The player name generation in the DefaultGameMaster class now uses this utility function to generate player names with the prefix "Player" followed by a number. This improves the readability and maintainability of the code.