Add problem Coin Change Problem II with test cases

[CosmicMagnetar]

• Implemented the memoized recursive solution for Coin Change Problem II.
• Function count(coins, N, target) calculates the number of distinct ways to make up the target sum using given coin denominations.
• Added 5 sample test cases to validate the solution.
• Followed the standard format used in previous algorithm implementations (problem description + solution + test cases).