refactor: divide command switch into smaller methods

This pull request refactors the Command class to improve code readability and maintainability by extracting command actions into separate methods. Additionally, it includes minor improvements to PlayerList and MatchList classes.

Refactoring Command Class:

• Extracted command actions into private methods for better readability and maintainability (src/Command.java). 1(diffhunk://#diff-55b91a5d613b340ad9761c4acbb61d8f43c5ebbc122ff2bc5c054f38441e92cdL26-R141) 2(diffhunk://#diff-55b91a5d613b340ad9761c4acbb61d8f43c5ebbc122ff2bc5c054f38441e92cdL96-L104)

PlayerList Improvements:

• Improved the remove method to store the result of the removal operation and assert on the result (src/PlayerList.java).
• Implemented the isEmpty method to check if the player list is empty (src/PlayerList.java).

MatchList Improvements:

• Removed redundant print statements from the show method (src/MatchList.java).