Create a function that returns true if smaller arrays can concatenate to form the target array and false otherwise.
canConcatenate([[1, 2, 3, 4], [5, 6], [7]], [1, 2, 3, 4, 5, 6, 7]) ➞ true
canConcatenate([[2, 1, 3], [5, 4, 7, 6]], [7, 6, 5, 4, 3, 2, 1]) ➞ true
canConcatenate([[2, 1, 3], [5, 4, 7, 6, 7]], [1, 2, 3, 4, 5, 6, 7]) ➞ false
// Duplicate 7s not found in target array.
canConcatenate([[2, 1, 3], [5, 4, 7]], [1, 2, 3, 4, 5, 6, 7]) ➞ false
// Missing 6 from target array.