refactor: clean up duplicate algorithm implementations to reduce maintenance overhead (#7256)

refactor: remove duplicate algorithm implementations

Removed the following duplicate implementations:
- searches/PerfectBinarySearch.java (duplicate of IterativeBinarySearch)
- searches/SortOrderAgnosticBinarySearch.java (duplicate of OrderAgnosticBinarySearch)
- strings/LongestPalindromicSubstring.java (duplicate of dynamicprogramming version)
- strings/ValidParentheses.java (duplicate of stacks version)
- others/cn/HammingDistance.java (duplicate - strings version handles text)
- others/NewManShanksPrimeTest.java (orphan test in wrong package)

Updated DIRECTORY.md to reflect the changes.

Fixes #7253

Co-authored-by: Ahmed Allam <60698204+AllamF5J@users.noreply.github.com>