Align Java public class names with file names

[Nullkernel]

Motivation

• Ensure each Java public class matches its .java file stem to follow Java language rules and avoid runtime/IDE/compilation issues.
• Remove multiple files exposing public class Main which caused duplicate top-level public class names in the trees examples.
• Keep repository consistent and make the codebase safer for compilation and packaging.

Description

• Renamed public class identifiers across sorting and searching examples so the class name equals the filename (e.g., DS_*/old names were replaced with Radixsort, Heapsort, Bubblesort, Insertionsort, Selectionsort, Quicksort_Lomuto, Mergesort, Quicksort_Hoare, Shellsort, Binarysearch, Linearsearch, Interpolationsearch, Uniform_binarysearch, etc.).
• Replaced public class Main in tree examples with AVLTree, BinaryTree, and BinarySearchTree respectively and updated in-file usages/constructors to the new names.
• Avoided multiple top-level public classes per file by renaming an internal example helper to BinaryTreeStructure and adjusting the main usage so the single public BinaryTree class remains in BinaryTree.java.
• Per-file edits ensure exactly one top-level public class and that its name equals the file stem for all modified .java files.

Testing

• Ran a repository-wide regex scan (python - <<'PY' ... pub_pat = re.compile(r'public\s+class\s+...')) to confirm there are no remaining mismatches and the scan returned STATUS OK.
• Ran the Java compile smoke test script (bash scripts/java_compile_smoke_test.sh) which compiled all Java files and reported success ("Java compile smoke test passed").

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Codex Task